I think cbi RON  is  red  john   because  :-
(1) Ron is very similar to  red john.Like R ed -jh ON.

(2) He's always there  ..behind every one   doesn't speak.As bruno heller said we've already  seen red john  many times .

(3)Red john knows everything  that happens in the cbi office. so maybe he works in the cbi office . And RJ has many times contacted jane in the cbi office  but  still he untraceable . AND  nobody can hack into cbi servers from outside.

(4) look carefully (4x13) when  RED john  meets rosalind harker.  he's sitting  like jane  and the  way  he's holding the tea cup ...just look at his hand he's wearing  a  RING  , it's blurry  but ron is also wearing same kind of ring.

Some people are saying that RJ could be his father, but why? I mean, patrick's father is (was?) a quack, why would he be killing people? and 'he knows patrick that well so he knows what he's going to do' but why would he wanna hurt him? plus, RJ killed Jane's wife and child after Jane insulted RJ on tv, so if Jane never said something about RJ, RJ whouldn't have killed his family. I think it would be a total coincidense if RJ is Alex Jane.

I do not know who Red John is, but I have a few things to say. 

1) The writers would be insulting the viewers' intelligence by revealing PJ as RJ. 

2) That Susan Darcy lady must have a skeleton in her closet!

3) At the end of the most recent episode, (5 x 03) did something not seem off to you when Lisbon goes to play poker with FBI and finds her boss, CBI director (Bertram) there too??! That scene has a weird vibe to it and I can see RJ having something to do with that gathering. Remember, RJ has a friend in the FBI. But I can't say for sure that Bertram is our guy because he seems taller than the guy in the mask in season 2 finale and because I don't see a director like that doing the dirty job by himself.