While I have been disappointed with the show post-Red John, its not because McAllister was Red John. If we had gotten more answers I would be fine with it. I'm also a fan of strong villains but the show was clear they weren't going that direction. 

As to the last episode being called "Red..." something, I think more likely the hidden title is "White." As in "White Wedding" between Jane and Lisbon. If by some chance the show does get renewed (someone can correct me if it has been officially cancelled), they have a lot of paths to follow after that.