Well we all know that there will be 7 suspect revealed...and shortly I would like to guess these 7 names:

-Osvaldo Ardilles
-Brett Pattridge
-Gale Bertram
-Robert Kirkland
-Ellis Mars
-Ray Haffner
-Walter Mashburn

Ardilless:
he is not really so much interesting, he is just a lawyer. But there are two reasons why I choose him: Cut Iron->In Court and a very special hint from the writers, that we should look for the anagrams, and Red sails in the sunset is an anagram for Hunt Ardilles,its seen.

Brett Pattridge:
He fits all the descriptions and is very known for investigating Red John cases. He appeared in the Pilot and in the finale of season 2. I wouldn't bet for him being RJ, but it's possible, since he and Jane hate each other and for the mirror scene in Red Sky in The Morning.

Gale Bertram:
We all know who he is but I believe most of you don't believe he is RJ because of Poker. I agree. but the most important thing, which I believe shouldn't be forgotten is:-He cares a lot about media(LIKE RED JOHN?) and the most interesting scene in the series : season 3 finale. when Jane meets him at the Mall, Jane, Gale, Rigsby and Cho are the only ones that know they will meet there. so how would RJ know that? Gale is RJ... Red John had to guide Jane to solve the puzzle, so he said at the end of the rope...interesting? yeah

Ellis Mars:
My personal guess because of the psychic thingy. The show writer said that the season 5 finale will turn the hunt for Red John in a new way and since it's at a carnival it's completely logical, since Mars is a psychic. Weird scene was, when he knew about Jane's tragedy and Tiger burning bright "card". it's either he is red john or he is accually a psychic, which is less possible.

Bob Kirkland:
Many people ruled him out since the hunt scene, where its shown that he has a same board as Jane, but bigger. There are 2 options:Either he is hunting Red John, either he is Red John and has a such desk for Jane. I would believe he was RJ if writers wouldn't make it so obvious.

Ray Haffner:
Interesting since Red Barn, but i would like to mention the fact, that he admited that Jane is smarter than him...RJ wouldn't.

Walter Mashburn:
He is "friends" with Jane and a former lover with Lisbon. it would be interesting seeing him being RJ and telling that him and Lisbon had sex, but he doesn't really fit the smart guy appearance. he is just rich.

My guess:
Ellis Mars:35%
Gale Bertram:30%
Kirkland:20%
Pattridge:10%
Haffner:2%
Mashburn:2%
Ardilless:1%


Important clues that everyone has to think about:
-Bret knowing about Rosalind.
-Gale/Jane scene at the mall
-RJ is a showman,puppet,mentalist,...
-Lorelei storyline
-Friend in the FBI
-Relationship with Jane
-Carnival thingy(Lorelei,season 5 finale), Hates pyschics
-Tyger, Tyger song

everytime a knew RJ fact comes out i get more confused ;/