I guess even after the series finale there will be people saying Red John is still alive. No one will be ever satisfied with an answer. McAllister (I think it was a great Red John, with lack of explanations, bad script and etc) is not good enough for some people. If it was Partridge, there will be a lot of people unsatisfied, if it was Kirkland, same thing, and the same thing to the rest of the suspects. 

People can't just accept the fact that the series is moving on, that Red John is dead. I guess even when the series is over there will be people like "Oh, Red John is still alive, its 'that guy', he was the mastermind behind every fuking episode and Heller want us to think he is dead".

This is just like the 5 Stages of Grief:

1 - Denial: People just cant accept McAllister as Red John;
2 - Anger: Fuck you, Bruno Heller! Your show sucks, you suck!;
3 - Bargaining: Well, maybe Red John is still alive, maybe McAllister was just another follower like Timothy Carter;
4 - Depression: (This is when people will realize Red John was indeed DEAD and it was McAllister, problably near the series finale);
5 - Acceptance: Looping on stage 1.