No amount of looking for clues in the show will reveal who red john is.  In order to figure out who RJ is, one must think like Bruno.  Its Bruno's Role to not give away who RJ is, and for us to feel like detectives.  The question is.....If you where Bruno who would you want to be Red John?  Additionally, when the show ends the creators will still want people to purhase the DVD's so its imperative in my opinion that the entire catalog of the mentalist tells a tale, just like william blakes poem.  I believe when we get to the end of the show, the entire work will reflect an entire idea, a philosophy.  I think something much more important will be revealed about Patrick and his journey of revenge.  Like in life, its never about the destination its about the journey.  It would be so cool, if PJ is actually in a mental asylum telling his story and a new series starts from there.