Okay so after the last episode I'm sure that it's not the three remaining suspects because it's too easy. I think Red John is more clever to be in the tyger tyger group. This group might be connected to him, might be his minions but he is above them and I think he wouldn't be stupid enough to have the same tattoo as all of them.
They might also be looking for RJ. Not sure about that but they might.

Ray fits the descriptions that we have of RJ, he has the right age and he is creepy. there is this vibe coming of him. When Teresa accusses him of being RJ he seems angry and offended but wouldn't that be a good reaction rather than to play it cool.
He has RJ' weird walk. He didn't really hesitate to take of his shirt which shows a bit of confidence that can be seen as either good or bad.
He likes Teresa and that could be why she is still alive. There is just something about him. I can't quite describe it but I like him for the part. Plus I hope it's him.