The only two suspects from Jane's list to appear in the episode Red John are the actors for Bertram and Smith.
Now unless they will hide the actor who plays Red John's name from the credits, then it could be basically anyone else.
But I read somewhere that the actor who plays Red John has stated that he thought he was a Red Herring and that he was in fact on the list.
Personally I really really hope he isn't on the list because it will be pretty anti-climactic.
Now if it is either Smith or Bertram, I'd opt for Smith simply for the reason that Bertram could not be Red John after the stunt that Jane pulled in Strawberries and Cream otherwise Bertram having concerted with his accomplice would not send his killer into the trap. Especially not to the room number he himself was given.
Smith is also, I think, a poor choice for Red John. There is no reason to exclude him though other that the fact the he is not old enough to have been the person drawing the smiley face after the killings at the visualize barn in 1988 (he would've been 12). But he is still more likely than Bertram to me.
