Actually I don't like these kind of theories but look at what Robin Tunney (Teresa Lisbon) says in her interview http://robingreenshades.blogspot.com/2013/10/interview-robin-tunney-shocked-at-red.html

"I was surprised, and had I been Red John, I would have been equally surprised"

If she was surprised this much, Red John is either someone out of the list or someone known to be dead.