Frankly, I think it's a little bit ridiculous to believe that Jane and Red John are the same person. Besides the fact that this is a television show, and the viewers' possible reactions to a certain plot twist or revelation are taken into consideration by the show's writers, the idea doesn't make any logical sense. The show itself is a procedural--a typical "who done it" mystery. I'm sure, at one point, the idea that Jane and Red John were one in the same crossed every one of our minds, making him, at least in my opinion, the least likely suspect. There have been constant little suggestions that Jane and Red John have similar personalities, that they could even be friends. It's little things like those that are designed to make us consider the possibility that Jane is Red John. And that would be much too easy considering the show's complexity. Ironically enough, writing Jane, the easiest of suspects, as Red John would be an extremely complicated matter. The details that would have to be revealed about each and every one of his murders and deceptions would be overwhelming and implausible--the show would lose its sense of believability. That being said, Heller himself mentioned in an interview that Jane and Red John are not the same person; it would be much too unfair to the fans that have rooted for Jane since the start of the series.
Regarding the real identity of red john: I believe that the idea is to surprise the viewers. I don't doubt that it could be any one of the more obvious suspects(excluding Lisbon and most of the CBI team, it doesn't seem very likely) but I also think it's wholly possible that it could be someone else entirely. The fun is in the speculation, the clues. It's been said that this latest season will be a big one in terms of Red John's identity, and I, for one, cannot wait to be surprised.
