My guess is that Red John is Bret Stiles and Robert Kirkland is Bret’s son and his helper.  Stiles has the intelligence, money and power to be able to commit all the murders.  Also, as a cult leader he definitely has a lot of influence over people, including women. Because of his age though he relies heavily on Robert to help with the physicality of the killings. 

Ok, this is me reaching a little bit, but with things like hypnosis and manipulation involved, you kind of have to.

Bruno said that one of the people on the list IS in fact Red John.  For a while, I have been like most people in thinking that Bret Stiles is TOO obvious...But after seeing the "final seven," I HAD to think that maybe it IS an obvious choice, but that the story behind it won't be obvious, and still surprise us.  Here is my fun logic behind Stiles possibly being RJ:
Bret Stiles is Red John...BUT he hypnotized Jane, making Jane the NEW Red John...One of the arguments against Bret Stiles is that he is too old, so perhaps he needed somebody to take over his Red John business and be his apprentice.Jane, being the master manipulator that he is, reminded Stiles of himself and he became very fond of Jane...Maybe after Stiles murdered Jane's wife and daughter, Jane went to visualize and Bret mentored him.  He then hypnotized him, and made him forget that he was ever a part of visualize.
This could also explain the "until you find me, or i find you..." from the video.Either Jane will find out about Bret Stiles being the past Red John, or Stiles will expose Jane as the NEW Red John and Jane won't be able to prove that Stiles had anything to do with it.
Side Not:  When Lorelei was reading the not from Red John, to me, it sounded like Bret Stiles speaking in the letter.  the whole "Bravo" and "you think you're clever?" stuff sounded like things Stiles would say...but who knows, the writers could literally make up ANY story for who is Red John, so it is impossible to tell.

I am sick and tired of any ass hole accusing anyone not on the list of 7 because it's not jane because he's not ton the list of seven and bruno heller specifically stated it will be someone on the list of seven so any one accusing someone not on the list shut up and go away https://www.dropbox.com/s/m01sqnq7xv9gysv/red%20john%20list.xlsx this is a link to an excel worksheet compiling data on the seven suspects and who is most likely red john take a look if you like

Okay let´s  focus on the facts:

1.RJ is a Serial Killer -a rapist before he kills and therefore  it´s a man.
2. he kills Patricks Family because he wanted to teach PJ that he is not so clever ("if you were a true xy you don´t have to open the door to see what I did to your Family...) and he did this because he felt deeply insulted be PJ´s interview on TV.
Which means RJ is really creepy - he also felt insulted by the San Joaquim Killer and acted the same way- kill the one who he thought insulted him.
He did not kill PJ because he has a sense of admiring PJ´s Cleverness-as long PJ isn´t smarter as he is.(for this admiration he send Lorelai as a "Love-gift" first.)
3.he has a huge Network of Co workers for him - especially middle aged women- which means he can attract women easily by charme, Charisma, Money what else.
4. He likes sitting next to Rosalind when she´s playing the piano - I think this fits more to an older guy like Bret Stiles.
Rosalind is safe because she is blind and she loves him- the Person he Plays for her. the fact that she is blind makes sure she is honest and can´t be attracted by his fame as Visualize head. also he makes sure that she is his Possession (remember the little Smiley on her wall)
Even the description of Rosalind fits- straight hair and the physical attributes.
5. the Smiley on the Red Barn doesn´t have to be painted by  kid only someone pressumed this. Fact is:  it was painted in the 80-ties by someone Close to "Visualize"- it´´s RJ Symbol like Visualize has a Symbol. so it´s RJ personal note.  RJ could be without any Problems now in his fifties..
6.  Bret Stilesknows that Lorelai is becoming  a future Problem when he helps PJ to free her from prison and he could be prepared  when she leaves his Network and hunts for him.
7. The man who was killed in the Hospital was a Close "friend" to RJ - so does anyone think Patridge could be so charismatic to womanize all that Ladies and rule to all the established middle aged man? It must be Stiles to my opinion. Kirkland is working for RJ. Aweful smile on kirklands face when PJ finds Lorelai....
8. "Visualize" Keep their Windows Close for Police Investigation so RJ is able to Keep undetected for a long time. He also thinks he can threaten future murders because he feels secure to rest covered among "Visualize".
9. RJ is a great Showman (like Stiles), he is really clever and manipulative (as Lorelai said).
His first choice is Power (he predicts the rules- in 5x22 PJ "changed the rules" and the threat has to be future punishment for Patrick- so RJ is in his daily Life in a powerful Position.
He is sadistic  and attracts sadistic networkers by letting them having their pleasures (the Sheriff son who hold the trapped rich Girl in the Basement of a barn and was shot by Patrick...) this means RJ has enough Power to make sadistic People submit to him (f.e by means of Money or whatever).And he likes to watch/study the dark sides of his workers...
10. he seems to be attracted to red haired woman (Rosalind, Kristina,Brenda, Rebecca and yes: van pelt!-look how charming bret Stiles is with Van Pelt...
11. in 5x22 when Lorelai reads the letter makes compliments with PJs work  and says "bravo"- it sounds like Stiles style...
For me all points to Stiles- only disturbing thing is: PJ teaching Betram lessons in poker Face... There Betram was unable to loose a poker game which reveals also a very vain and power possesed character... this is my suspect number second- also I think Bertram doesnt have enough Charme and Power to make all these people work for him.

 

Let me start by saying this:

1) If it's Sheriff McAllister, I'd be dissapointed. We haven't seen him since s1 e01 - as much as he was a hardcore creep to Van Pelt... no. 

2) If it's Reed Smith...wait...who's Reed Smith?

HOWEVER, I could honestly see the rest of them (with, or without Partridge) being connected. Stiles runs visualize, of which Ray Haffner is a member. Kirkland and Bertram have a connection through the promise between Kirkland and Minelli to stay in touch about the case. They're all high-rank individuals, in one way or another.

Not sure about Partridge. He's no mastermind - he may be another tool, though.

I believe that Red John could be a lot of people. The guy at the end of the third season who Jane shot could actually be the guy who killed Jane's wife and daughter. And all of the other murders could have been done by other suspects as well. But I think that Bret Stiles organized all of these people to kill by brainwashing them like he does with the people at Visualize. Ultimately Bret Stiles has organized his own group of serial killers to do anything he wants. That's my theory. 

I think It is Bret Stiles because he ha been involved in many of the Red John cases.