Looks like the thought on everyone's minds is, "Is RJ with Tiger, Tiger, or he isn't he?"  This is tricky but I have a few reasons why I feel RJ has to be a member.

1.)  He Is Mar:  The best answer I have for what Renfrew wrote on the wall in season one is He Is Marked.  Therefore, it stands to reason that RJ's mark might be the tattoo.

2.)  The Poem:  Red John quotes the William Blake poem to Jane waaaaayyy back in season 2.  I don't think he said that to Jane four seasons ago just to throw Patrick onto an organization he has nothing to do with.  He was teasing Jane with this statement.  It was like, "I dare you to figure out what this means."

3.)  Red John's Friends:  We know he's got a lot of them, many of which are in or around law enforcement.  O'laughflin, Sheriff Ted Hardy a.k.a. Dumar from season 1, and Bosco's secretary in season 2, who was incidentally poisoned by a sheriff.  He even tells Patrick in season 4, "Luckily I have a friend in the FBI".  I doubt there are two secret organizations within law enforcement.  Occam's Razor states "The simplest solution is always the best one".

4.)  The Bomb:  I feel like the bomb might explain the bugging of the CBI.  Red John has purposely thrown Jane onto this trail.  He allowed Kira Tinsley to see his tattoo so Jane would bring all the suspects together.  Once they were all together, RJ planned to use the bomb to kill Jane and the other suspects, just as Rigsby states in the promo for next week's episode.  

If blowing up Jane and the suspects was his plan, then RJ is probably the Sheriff, because he's the only one who happily wants to meet with Jane.  It would also explain why McAllister was so calm when Jane was interrogating the 5 of them.  It was all going according to plan.  The bomb will probably kill a few suspects, and the CBI will be left wondering who survived the blast allowing RJ to go into hiding.