My theory is this.

This whole show is a dream of some sort that Patrick Jane is having.

I think Patrick is actually still in the mental hospital from his mental breakdown from his wife and daughters murder and he is delusional.

It just seems so impossible that one man, Red John could be behind all of this. 

I really dont hope this is true though.

If this was not true, I would have to say that Red John is Ellis Mars. The actor that plays him, John Billingsley, has played serial killers in other shows such as Cold Case. He also has a high fucking voice. Another reason is because of the HE IS MAR shit. 

Another reason for Ellis Mars is that the episode he was in, "RED MOON". Mars, his last name, is referred to as the RED PLANET.

idk, but im still sticking with my first theory.