I personally think that Red John is somebody that we know, maybe in the background a lot or a regular? I don't think that the writers have fully worked it out yet, they probably have a list of people that it could be, and are just trying to work it out. It can't be Jane, that would just be annoying if it was and I would hope that Lisbon isn't a partner of Red John although would be a good storyline if she was. :)