well, i think it can't be kirkland, when kirkland and jane shook hands, lorelei was in prison, probably unaware of the outside. 

but gale's picture on the wall with that weird zoom out effect while jane and kirk were shooking hands, that was a little bit creppy
but gale is taller than rj,


i believe that van pelt and stiles are also involved with red john, somehow. they also have that "red smooke" manipulation thing
i mean, it seems like they have been avoiding grace and wayne as a couple again, i don't know but she is the most likely for being in rj group, maybe the newest one...


not so sure about Partridge, jane doesn't like him, maybe he was the very first option for being rj, or maybe he still is, i don't know.

CBI Ron is also very suspicious and once i read about a theory with the name Ron, and some kind of anagrams, we know the bruno loves anagrams.
He has ben a Reccuring Extra Through all of 5 seasons, and there is this note i read in a site: 

He is always around when the team is working, and knows the ins and outs of the CBI.1) The RJ appareance. Red John is like Waldo, on background, as says Bruno Heller, and we have already seen him

it could be him! maybe, someone who is always around.