Of course he is not! First of all it would ruined the main character of the series ( a hero). Second thing as we saw in the 3rd season RJ and PJ were in the same place at the same time, and the most important argument is that if PJ really has such mental disorder (schizophrenia etc.) he wouldn't be able to control it, so obviously his CBI "friends" and employers would recognized it imminently. Directors wants that at beginning of season 5 majority of you thinks of PJ as RJ and that is the strongest argument why he isn't the RJ!
Sorry for English