It might be Patrick's father Alex.
He hasn't been on the screen that much, but he had some appearances.
Red John is good at manipulating people. Alex Jane used to be a psychic, together with Jane. And 'Tiger, tiger' might have been a poem he used to tell Patrick when he was young. 
I can't think of a motive for being Red John, but he might have been angry with Patrick for something that has happened.

I was thinking that perhaps Red John is no one that we suspect. That in reality he didn't really kill anyone. That he uses or manipulates people into killing for him. This leaves a huge door open when he is caught, because they can't actually pin any of the murders on him. Then also, I was thinking that in the end of the season it would probably be very interesting if Red John kidnapped Agent Lisbon.  

I believe it is possible that Janes's wife and daughter are not really dead. They somehow managed to escape RJ and are now on a protection program and must stay in hiding until RJ is caught. It is as if they are dead for Jane however as he cannot contact them or even know where they are. This would explain why there are no birth or death dates on their grave stones.

"He Is Marksman"; it's Max Winter; after murder of his wife Jennie Winter,  his wild, revenge hungry,sub personality(RJ)was born; that personality is reconciled inside him with 'normal' Max, who for sake of his son Jackson is same as before tragic event;

I
 think Sarah Harrigan is RJ or a disciple. If only a disciple, then the baby is probably
RJ’s not Waynes. This will come to light at season’s end when Sarah is
exposed and the truth comes out. Wayne will then be free from a
relationship he did not want and free from fatherhood to pursue Grace
again. This is a parallel to what Grace went through when her “love” was
discovered to be an RJ operative. The cast and story lines are too
clutter with extraneous people and relationships that don’t move the
story forward or add drama/suspense.

Apart from Lisbon and Lorelei, all of the other female cast members who are current suspects have red (or reddish) hair, Grace Van Pelt, Kristina Frye, Rosalind Harker, Susan Darcy, Brenda Shettrick, even Madeline Hightower. Summer and Sarah (Rigsby's girlfriend) don't have red hair but I don't think that they are in the show as suspects, just there to add to Cho and Rigsby's storylines). Could it be possible that the red haired women are all in some way linked to Red John and that he chose them because of their red hair? I don't believe that Grace is Red John (too young) but could be linked in another way, possibly through family. Kristina Frye is a victim of RJ and may even be RJ and pretending to be in a catatonic state to escape suspicion. Rosalind Harker also has links even if Roy Tagliaferro is not RJ. Madeline Hightower was also linked indirectly through Todd Johnson but we have no more news of her. I don't know how Susan Darcy or Brenda Shettrick could be linked but it seems that this is a disproportionately high number of redhaired women in the cast without a specific reason, especially since none of the male suspects have red (or reddish) hair. Minelli, Bertram, Laroche, Brett Stiles could have had red hair before going grey but we have no way of knowing this and no indication has been given that this is the case. The other male suspects, Bret Partridge, CBI Ron, Walter Mashburn, Luther Wainright and Craig O'Laughlin are dark haired and Patrick Jane is fair haired. It seems to me that the red haired women are all linked to RJ in someway or another or are otherwise there as red herrings.

Bob Kirkland is a red herring. He may seem suspicious but I believe he is following the Red John case himself and trying to find out if Jane is actually connected, because I think RJ is going to frame Jane to make it look like RJ is Jane but really Bob Kirkland will help Jane.

That's a prediction of mine. And I would like it if the story played out that way