I always thought it was Jane, and after last night's episode I'm almost sure of it. I think it's possible that Jane doesn't even know that he's Red John, like he's schizophrenic or something. RJ's always 2 steps ahead of Jane; all his accomplices talk to Jane like they know him and also the way they look to him when anyone asks them about Red John, with a hint of fear; in the latest episode "Red Dawn" which flashed back to when Jane first started working for the CBI, FBI agent Alexa Schultz calls Minelli and tells him that he should know that Jane was in an insane asylum for a year, this set of all the alarms in my head. Also, RJ always knows whats going on with the team, like he's on the inside.

If it's anyone else it just wouldn't feel right. Then again this might be the point, maybe the writers and Red John are setting it up to look like Jane's Red John, even make him believe it and doubt himself, since that's what the show is all about: mind games

If you happen to read Carl Jung's Red Book, then this will explain everything. Jane's mind created this world of hallucinations, self-induced hallucinations. We can see the character reading Carl Jung's book in select episodes. This is a story of person's journey to the unconscious, where he (the mentalist) creates a world of "what ifs" and begins to formulate his own solution of the struggles faced within the imaginary world.

RED JOHN is in Fact PATRICK  JANE it is his altar / EGO

Red John(RJ) has to be Patrick, there is no one intelligent as him as you all know patric is brilliant and knows without them speaking.patric never uses gun and guess rj uses knifes never a gun. he cannot read rj friends because he himself hypnotises them and in rj friend episode why did jared contact pj since he is friend and how does rj know jared's location and you should be amazed what ever patrick knows rj also knows them how, how come there is recorded message to luther and luther is another person who thinks patrick is rj so he kills him in the mission by manuplating everyone. only doubt i have is does he know he is rj or he lost his one half as he saw his family die, he was also hospitalized for his mental illness.there is no coincedence but i will be happy if rj is pj and season 5 is gonna see pj's dark side. 

Here's why I don't think it would be PJ.

Think about the ramifications of Red John turning out to be Patrick. It would be a defense attorney's dream. Every single case that PJ helped clear over the course of the show would immediately up for review and retrial. Almost every defendant and their attorney would be able to claim that they were framed by PJ/RJ.

Don't forget shadow of doubt here. my defendant was framed by the notorious serial killer Red John, who happened be a consultant for the CBI and worked directly on his case. would any jury need more than that to acquit.

What about evidence, every piece of information or evidence that PJ helped them obtain in the course of an investigation is now suspect and most likely wouldn't be allowed in a new trial.

PJ turning out to be RJ would kind of be a betrayal of the whole series. This all works equally well for the lisbon theories.

Lets not forget the careers of every member of that team would be effectively over. Can you imagine the final scene of the series with the head of the CBI congratulating Lisbon and her team on capturing Red John and in the next breath placing them all on suspension pending an internal investigation.

Red John is known to have accomplices. If PJ turns out to be RJ would anyone believe that the members of Lisbons team were not accomplices. even if they were cleared that specter would follow them for the rest of their careers.

PJ as RJ would be the worst ending to the show.

When James shot the sheriff, his dyeing words were Red James Shhhh (and you thought I would say "but he did not shoot the deputy")....then they showed a simple cup of tea; PJ's signature...
Same premise as Sherlock Homes being Moriarty. Not too original.. but very poetic.

I think patrick jane is rj as he is never killed by any of his accomplices. I think he already killed rj but uses his names to do justice and kill everyone who is evil and thus everyone who gets close to jane personal life gets killed as he doesn't want anyone to look up his past history before joining CBI.Never dates anyone and there is no love life indicated by the writer for jane, how many Tv series has a lead with out a personal life or even one GF.