Unfortunately, nowhere does it state Red John has -returned- for episode 20, just that Jane may be going to trial for his murder. This is not to say that Red John may be returning, but based on the summary it may be simply to get the closure on Red John we have been looking for, at least that. This means that, during the trial (if it occurs), we may get an explanation for some of Red John's clues and actions. Then again, it may just be a half-assed cop-out from the storyline, again. I'm more inclined to believe the latter.
I'm baffled as to why some of you still have faith in Bruno Heller to deliver something spectacular.
A few things may happen here:
-Jane may create another ruse to avoid the trial altogether
-Jane may come up with another heartfelt speech to win the favor of the jury and get a verdict of "not guilty" (as he did in the beginning of season 4)
-Abbot may hold to his agreement and find some way to create a mistrial
-(very unlikely, but hoping)The real Red John will engineer something during the trial to void the charges against Jane and renew their game, or something similar. As far as this idea is concerned, though, it is operating under the assumption that Red John successfully framed Mcallister and has retired from killing for some time now, and Jane's trial would rekindle Red John's narcissism since he wouldn't actually be dead, forcing him to reveal he is not dead, which is why this is 'very unlikely'. Also, Heller doesn't seem capable of something like this.
All in all, my personal expectations are not high for this episode. There is only so much that can be done in three episodes you see, and the producers of The Mentalist aren't exactly masterful at showing quality and progression in a short amount of time (just look at the Richard Heibach BS). Whatever you may believe about this episode, you have to agree that deep down inside, you know it will probably be much less than we want.