I'm not going to explain why I think it's CBI Ron, because everybody has already given all of my examples...But I'm just going to give what I think would be a cool scenario for the rest of the series:

What if, at the end of season 5, Red John uses all of his resources to frame Patrick Jane and make everybody think that HE is Red John(even the fans of the show) by making all of the evidence point to Patrick...Then, during the trial, something is said that sparks a thought in Patrick's brain, and he figures out who RJ is, but he needs Lisbon to bust him out of jail so that he can prove who the REAL Red John is...of course, everybody will be trying to hunt down Patrick after he escapes, and finally, with 100 guns drawn on Patrick, he does one of his fancy tricks or whatever to explain who is actually Red John, and then they arrest him....(this 99% probably wont happen, but I thought that would be kind of cool)