I'm a huge fan of the show but I do believe it needs to be cancelled, whether they do something unexpected before it ends or not.
 
The past episodes have been awful on their own, a mish mash of Jane's old tricks and faces, with no inherent mystery or interesting plot.

Even if they lead to a big reveal (doubtful) there's just no excuse for their quality. One can't go: Hey see this guy? He was RJ/ Santa Claus Keyser Soze all along and call that a good twist.

Let's take an example: Let's assume that this Marcus Pike is the real real real Red John (even typing it at this point looks ridiculous). Let's say that on the season finale he is revealed. Hell, let's assume he is revealed on the very next episode.
 
Will that retroactively make the previous abysmal episodes any better? It won't. They'll still have poor writing, plot and no character development. If you doubt it, try picturing that Marcus Pike is 100% RJ and rewatch the past episodes. It hardly makes any difference to their quality.

A good twist relies on interesting things happening ON screen and when the twist comes, it can be explained partially with some things happening off screen and a lot of hints and behaviours ON it. You can't just have NOTHING happening on screen and leave EVERYTHING happening on the background where the viewer does not see them, That's has an official term, and it's called "pulling something out of one's arse". That's lazy, bad writing.

A show that relies on a "9 horrible episodes then 1 great" is not a good show. It's M. Night Shyamalan's cinematic biopic.