I think RJ is a group of 2 people: Kirkland and Haffner.

Maybe they are brothers or something and they are both mirderers, they give info to each other one from visualize (Haffner) and the other one from the FBI (Kirkland).

If I get 10 plausibles ill give you more details.

Right now I am convinced that none of the people on Jane's list is Red John.Why?Because he says "I recalled all the names of the 2164 people that I met and shook hands with since Red John murdered my family" which means none of the names on that list are people before his family died.
Now, not that I am sure Red John and Patrick knew before his family murder, but the simple fact that he didn't take into consideration to count people before that event settles it.
The plot will go like this, Patrick comes closer to Red John(or so he thinks) ruling out the names on his list one by one and when we are finally close to him(like there are only 3 or 4 people or even only one person) we will find out that he's not Red John.Why?Because it's a sure thing that the show will go on for at least one more season after season 5.Actually I heard rumors that the mentalist was intended to be a 7 seasons show.My point is that obviously, season 5 is not the last.So this whole 408 hundred names list is another ruse of Bruno Heller to make us interested in the show because it involves Red John, but actually it will be revealed as another fake lead.Like how Heller revealed us Red John at the end of the third season(Timothy Carter), had Patrick killed him right then and there only to find out he wasn't the real Red John, but one of his many disciples.
The reasons I believe this(aside from the fact the show will continue after its fifth season) are Patrick's certainty that Red John is a man he met after his family murder which is not 100% sure.I am not saying Red John is his father, but you can't be sure of that.For all we know Red John and Patrick met when they were teenagers and shook hands at the carnival and RJ was reminiscing about that when he told Lorelei, something like "Maybe we were destined to be enemies.Because we met long before he slandered my name in the media forcing me to teach him a lesson.First time I met him I was with my family at this carnival and there I met this kid who knew some cool magic tricks.After I shook hands with him, he said his name is Patrick Jane and he was there helping his father with the business".How do you know it wasn't something random like that?Or maybe he was an old client of Patrick.Or maybe he is Danny Ruskin, his brother-in-law.Recently I've seen a lot of theories about him being Red John and some of them are quite logical.So the simple fact that Patrick excluded people he has shaken hands with before his family murder means there's a good chance none of those people on his list is RJ.
The other reason is what Patrick says afterwards "I might have missed one or two, but not many".There you have it.Patrick himself admitting and realizing that the list is not complete which means Red John might not even be on the list.Knowing detective shows and the fact that this one is not ending this season, I say there's a far bigger chance that Red John is one of the people Patrick missed.Even if Red John is on the list, how does Patrick know he can't be one of those 949 men he had brief encounters with and never saw or heard from again?After all, we know Red John met and shook hands with Patrick and despite how similar they are, they didn't become friends.So it's very likely Red John is one of those 949 men that only met with Patrick once and that's it.
And what about what Lorelei was saying?I mean, she said "I'm surprised you two did not become lifelong best friends when you shook hands".We know Lorelei wasn't lying because she said that when she was angry at Patrick, so obviously she hasn't realised what she said.But how does she know that?Because Red John told her.And what if Red John lied?Think about that for a second, what if Red John lied?He had no obligation of revealing this piece of information to Lorelei, maybe he told her this to appear he trusts her more than he actually is.After all, we know everyone of his disciples are just his sacrificial pawns.The only way Lorelei can be sure that's true is if she was there with Red John when Patrick shook hands with him.But she wasn't.Unless you say Red John is one of those two guys that show up when Patrick spoke with Lorelei for the first time, one of them was a rich guy who paid Patrick in order to speak with his deceased mother and then when he learned that his mother was actually alive, he came to take the money back or to punish Patrick and the second guy was his bodyguard who beat Patrick to a pulp.I don't know about you, but it's obvious none of those two were Red John and he's not even shaken hands with one of them so Lorelei has no certain way of knowing that Red John and Patrick actually shook hands and that it wasn't a lie.
My point is that in the end there's no certainty that one of those last 408 names is Red John.Actually there's no certainty that Red John even shook hands with Patrick because obviously Lorelei wasn't there when it happened, Patrick would've remembered if he shook a guy's hand and Lorelei was there with said guy.
Obviously the plot will revolve around that list and around season 5 finale we will supposedly get closer to Red John as Patrick's list will only contain like 5 people or so and maybe we will even end the season thinking Patrick found and killed Red John only to learn at the beginning of the sixth season that it was another ruse of Red John to play with Patrick.Something like RJ finding out about Patrick's attempt to catch him and fool Patrick again.The fact that this is not the final season of the mentalist proves it.

This is more a summary of my top suspects 

-Brett Partridge: There is a lot of good evidence supporting him as RJ. Some may argue he is too young, but that is not the case. I won't rehash what evidence has already been said but I will add that in the pilot when Jane is describing why it isn't RJ, Partridge looks very uncomfortable and we assume it's because he is getting called out by Jane. But if he is in fact RJ his discomfort can be explained in that he is surprised how well Jane understands him. Thus this moment is the start of RJ's liking toward Jane.

-Redshirt guy- The guy in the finale of S3.

-CBI Ron He's in the background, always there, we don't know much about him. Very well could be RJ.

-Kristina Frye- She is my oldest suspect so I have a hard time dropping her. While everything is making it almost certain RJ is a man, if the writer's throw in some kind of twist that could explain RJ being a woman, then it's K Frye for sure.

My other explanation would be
-RJ is 2 people (not an entire organization: This would clarify the rape of Lorelei's sister (I don't believe RJ would rape a victim)
-The writer's will throw in some curve about RJ when he is revealed that will be impossible for any of us to have predicted (like RJ is some long lost brother)

Who RJ is NOT
-Robert Kirkland
-Roy Haffner

I don't know why so many theories point to these guys just because they were made to look like suspects in recent episodes. The Mentalist never has the obvious person as the culprit. For example, S3 finale, of the 5 suspects, LaRoche and Bertram were the ones made to look like RJ's man, but neither were. Also see every other episode of The Mentalist ever for proof of this.

Im not here to submit a full theory but rather to point out an issue
pertaining to the bloody word written on the wall in the Mexican Motel.
Why is everyone assuming that it is 'He is Man...'.

Have you considered that the least letter might easily be an 'm' or an 'r'??and that the dying man was not able to completely form this last letter.

Do you agree? and in this case, what can the sentence truly be?

It is now concrete, although obviously was that RJ was or is connected with visualize. I mean when you listen to Lorelei speak about him and how he was able to help her set herself free...visualize crapola talk...like all religious cults. So RJ was a kid working on a farm where he was training to be a killer by first mutilating animals...then killing his first 2 victims in that basement in the barn.  Leaving his smiley face mark for all to see...he is not in the CBI...he isn't Kirkland...so this is how this season ends...Volker works a deal because he probably knows who RJ is...we get very close or maybe even see RJ as he is in the finale..RJ kills Volker...then dissapears...just seconds before Lisbon and Jane make it to stop anything.. Kirkland goes to prison...and that ends S5...still nothing resolved...except now we know who it is...but he will be untouchable till the middle of next season where Jane will have to figure out someone kind of manipulation to bring him back into the light...

The first clue he is man...clearly meant to be he is many otherwise why on earth wouldn't he just write out the name. A couple of other people have mentioned the cult being murderers. I think its unlikely the whole cult is in on it. That would be impossible to hide. But its very obvious from various episodes that red john is mentoring serial killers through an organization. So I think brett stiles is definitely in on it. Also a coincidence that bret partridge has same name.. how many people are called bret! The two are clearly linked to red john and yet neither has shook Jane's hand. I think the theory that Brett knows red john is clear perhaps even schooled him. The whole business of red mist and cleansing yourself its an easy leap to think brett stiles has developed an ideology that consists of murder as being a rite of passage. Add in the poem of lion taking his rightful place amongst the lamb.
So visualise is involved its likely brett knows who it is via the cameras that record everyones secrets but would rj wouldnt be that stupid. But brett has to be involved he is the only person with that amount of clout. I think it may be the guy who tried to stage a coo in Visualise. He drinks tea, has shook janes hand and fits the description. The voice is an issue but lets face it that's probably put on. Either that or what about that creepy little guy who gives jane a globe reading he appears in a couple of other episodes and his voice is pretty creepy. Also the most hilarious part is there is a lawyer in visualise called john.. XD
In terms of end theory bruno heller wants to get another two seasons out of this so, i think at least for season 5 we'll probably catch somebody. Either van pelt shows different colours or jane finally finds out that theres a network of serial killers...also jane is not red john that would be beyond stupid and totally implausible. 

The man we are looking for is JASON COOPER, yes the guy who we have been told is weak (in the episode about Visualize where a guy wanted to take over this group). That was smart its like no one have had mentioned him in theories.

In my theory Stiles is just a puppet of Cooper just a face and that show was just for keeping us away from Cooper beacuse who would even consider a guy who fails on his mission (that wouldnt be so red johns).

In last episode he is fully back like nothing ever happend and lets be honest - producers have to choose someone who already appeared in some episodes not just one or two that would be stupid and make me feel like i wasted time watching this (imagine a situation where red john is being revealed and he is totally new person and only Jane is like OH ITS YOU I HAVE MET YOU WHEN I WAS 2..... stupid)

plus he is old enough and he lives in a shadows (behind the scenes he is the head of the visualize and just use stiles to show his power)