I have read a few theories based on the fact that 6x08 only guest-starres Michael Gaston (Bertram) and Drew Powell (Smith) and therefore one of the two has to be RJ.

http://thementalist.wikia.com/wiki/Red_John_(episode)

But do you really think that if RJ e.g. was Partridge, they'd put Jack Plotnick on this list weeks before the episode airs? They'd give it away if they did.

Also, compare the guest-starrings of 6x08 (three names) to the one of e.g. 6x01 (eleven names) then you will realize that the list is not complete yet and names will still be added.

So IMHO, the two names being known to appear in 6x08 is rather indicating that the two are not RJ. Maybe they are part of the upcoming story. Remember that the show is not over after 6x08 and the writers need to come up with something to keep people interested (which will be hard I guess).