Hi everyone. What I am about to tell you isn't a theory much based on the series' plot, but on facts sources related to the series have shown. The reason I did that is 
because the writers' intent to give red herrings and stuff is clear. Therefore, I believe my line of thought is less prone to any twists on the plot than theories 
related to 'it has to be him because he was there from the start' or 'Mashbourne first appears in "redline", it must be him!'. BTW, seriously, stop with the suspect-
outside-Jane's-list crap. Heller has told millions of times RJ is one of the 7. While I'm on it, please, stop saying RJ is such and such because he's at IMDB's cast for 
the 'Red John' episode. That thing is user-edited. Good, let us proceed.
To me now it's pretty obvious RJ has to be either one of Brett Partridge, Bob/Michael Kirkland or Ray Haffner (I don't think it's Stiles, especially now that he's 
really dying (http://www.tvguide.com/News/Mentalist-Fire-Brimstone-Recap-Jane-Red-John-1073216.aspx)). Something I hadn't noticed till yesterday (and I know you guys 
are gonna say it's nothing, but I don't think they'd be giving misleading information like that):On CBS' The Mentalist page, under "Who is Red John", we can see all 7 suspects, including their names (from that, I believe it's safe to say we can cross Michael K. 
from that list).The other think we see is a cross on both Partridge's and Kirkland's pictures, meaning they are now excluded as suspects (that's at least what the site indicates). One could say people who update the website don't have access to that kind of information (and therefore couldn't know whether the information they're giving is 
misleading), but I think Heller/someone wouldn't have allowed that, if it wasn't true.That, plus http://cliqueclack.com/p/mentalist-brett-partridge-really-dead/?utm_source=web&utm_medium=clakus&utm.... if trustworthy means one of two things: either 
Partridge isn't RJ or he is and RJ is dead (why would he arrange his own death?).

****SPOILERS AHEAD****

That said, there's also the TV Guide thing, discussed on IMDB forums: 11th November's TV Guide (http://s22.postimg.org/7n1s3h529/Screenshot_13.jpg) tell us the following about Red John: "The actor playing him says he was 'stunned and flattered' when he learned that his character - one of the seven final suspects (n.b. see? Heller didn't lie to us!) - was the show's big bad. 'Earning this little place in pop-culture history was the last thing I ever expected.' he admits. 'Truth be told, I thought I was a red herring.'. Well, if I were Jack Plotnick (Partridge) and recently found out I was Red John, I would definitely not say this is unexpected. On the contrary, I'd be surprised if I wasn't RJ (pretty much everyone's guess since season 1).Guys at IMDB had some research and found out that only the actor (among the 7) that constantly uses the expression 'Truth be told' (vide https://twitter.com/reeddiamond/status/67426192172650496). This isn't a definitive answer, but I'd say it's a pretty good clue.
One last thing: not related to RJ, but we already know what happens on the 24th: "When the series leaps ahead two years, Lisbon is a small-town police chief in Washington (the state, probably); Rigsby and Van Pelt have two kids and run a detective agency (so that's how they're leaving. No one's dying or anything); and Cho is with the FBI". So that's how the series will run from now on! Can't say I'm dissapointed.
I hope this clarified something. Am I completely wrong? Please discuss!

alright I could be wrong here, but it is just a thought, Since the eigth episode is called "Red John" and based on the promo we have seen for the episode this upcoming sunday... I say it is quite possible that red john is revealed at the end of this episode on sunday night.  The following episode will show exactly how he operated all these years and answer the questions we need answers too.

It explains why past actors are back in the red john episode (flashbacks)  and the episode description says patrick comes face to face  with red john .... it does not say we don't know who he is beforehand.......

anyway just a thought....

To all those Kirkland Theories out there, I'm not here to slaunder you, but what I think speaks against him is that Kirkland and PJ shake hands when Lorelei is already in custody, and ep wise, it is only 1 episode before PJ with the help of Stiles gets her out. Now I know RJ has many helpers, but how what this conversation be? "How are you Lorelei? Oh I shook hands with Patrick the other day"... That seems highly unrealistic to me and imo points towards that Lorelei doesnt know they shook hands, ergo it can't be Kirkland, right? 

Nevertheless I cannot wait for this finale. My guess is Ray or the Sheriff, I cannot put my finger on why, of course there are also things speaking against it, but it's what my gut tells me.