Here is my theory going into the final two RJ episodes:

Jane has the 5 suspects in his house.  RJ planted a bomb under the couch.  The 3 TT members go to the wall at Jane's command.  The bomb kills Stiles and Haffner.  Jane has a hunch that the Sheriff is RJ during that reveal but was thrown off by the multiple tattoos.  After the explosion he devises a plan with the team saying he is dead along with Stiles, Haffner and McAllister (as seen in the promo).  But the promo also states that there are 3 suspects remaining, the TT clan.  The Sheriff is the only overlapping character.  Jane and Lisbon will make the public reveal that RJ is Bertram or Smith (while the real RJ, McAllister, is incorrectly presumed dead.)  This forces a manhunt t by all FBI/police resources to the fake suspect while Jane hunts the real Red John.....Sheriff Thomas McAllister.  The new episode 8 promo photos might be showing this hostility from the FBI at Lisbon's team after this reveal.  Maybe they realize that Jane is leading everyone on.  Let's face it, Jane WOULD NOT reveal the true RJ to the public so that he could be arrested.  He wants revenge, and he will get it.  This scenario is similar to drawing RJ out in Blinking Red Light and Panzer.

As one theory here stated, the narcissistic RJ will reach out to Patrick for his yearning for friendship and to say "Hey, NO! I'm RJ!" 

This is all based upon what we've been given in the show and promos, plus the TV Guide leak. 

The Sheriff is the ONLY suspect to have a full episode dedicated to him alone this season.  It was to further develop the on screen character of McAllister, as many including myself had a Who/what? moment when the list was revealed in season 5 finale.

Bertram could very well be RJ and was always my favorite, but the relationship angle brought about with the Sheriff just seems too good.

We'll see!  Super excited for these episodes!