Now, what everyone seems to forget when disapproving the theory that Jane could be Red John is that he does not have to be Red John all the time.
Most arguments used to disapprove this theory are that they cannot be at 2 places at once.
Now, what we have witnessed throughout the past 5 seasons is that RJ NEVER does ANYTHING. he has people doing it for him!
Now if I was Jane/RJ and I wanted to keep this a secret i would certainly too make it seem like i as jane was at one place while RJ were at another, to rule this theory out. keep in mind that Jane is one of the smartest people on this show - he is very intuitive, and he is always one step ahead. why wouldnt he be one step ahead as RJ too?
He definitely cant be ruled out - i thought so when lorelai said that she would find RJ (she said this to jane) but then i realised that up until then it has never been the real RJ it has always been someone in place of him. maybe the person lorelai thought was RJ was just another stand-in. 
remember that if it really is Jane you would have no way of being sure - he's that good.