There are a few other possibilities as well: 

1. The leaked episode is a fake, just to mislead us. Maybe Sunday will give us a different ending altogether. Different ending, mind you, not a different episode.

2. The leaked episode is the real deal, and if so, then maybe McAllister is NOT Red John! He may be another Timothy Carter, pretending to be RJ! The reason I think so is because this is just the 8th episode of the season. If RJ dies what happens in the rest of the episodes? Mentalist without Red John? :(

And also, the way the sheriff was killed was stupid! I don't think Heller will kill his creation of six years in such a manner. I hope not.

If the second point is true, we might see a 'resurrection' of Red John in the 9th episode or maybe later on. Maybe that is what forces Jane to get back into law enforcement. (I read thats what happens in 'My Blue Heaven'. I'm not sure.)

Whatever happens, I don't want the Red John saga to end this way.

Your views are welcome :)