This is probably unlikely, but I'll go for it.

I'm not sure who red john is but I'm predicting that perhaps as the list of the RJ suspects starts to decrease until there say, 2 suspects left, RJ will strike again but this time the victim doesn't die, or doesn't die immediately so they can give all the information PJ needs put together, and RJ will not be one of the 2 people, but someone who we'd never suspect, but has always been on our good side, which will have us shocked and talking for days.