Look at Heller's interview to Hollywood Reporter:

On whether Red John's disciplines will take actionHeller: Never say never, but I would say the audience and the story demands that we step away from that trope for a while. The trouble with these stories where you're playing tricks on the audience with "Who is it?" mysteries is that you can get way too mysterious. And there were a lot of people who said all the way along that Patrick Jane was Red John. When you've got that kind of elaborate thinking out there, it's dangerous to come back to stories unless you're coming back to that story with full force, because people will start thinking "Red John is not dead!" Red John is dead.

So I guess this is it guys.

To see the complete interview, go to http://www.hollywoodreporter.com/live-feed/mentalist-red-johns-fate-revealed-659592