I have so many theories it's unreal.

But I know for fact people that Red John is not Jane.

1. Why would he murder his own wife and daughter. Then be out to get himself!
2. When Rebecca was poisoned, Jane was with the others at the time, so how could he be in two places at once. Besides which Rebecca would know if Jane was Red John.
3. When he visited the blind woman Rosaline, she again would know by his voice if he was.
4. The man that spoke to Patrick and pulled him up on the chair was Red John, so how could he be speaking to himself.
My own theories on who he might be.

Danny Ruskin - TOP SUSPECT.

Reason 1. He hated Patrick for taking Angela away from him. Jane said she wanted to get away from the carnival life, however what if she found out something that scared her about Danny.

Reason 2. Cho said that Danny worked on the carnival and had a act like Patrick. Is this now Red John came to light.

Reason 3. The Name Ruskin means "red haired one" just type Ruskin meaning into Google.

Reason 4. The blind girl said Roy liked classical music. Maybe this is because Angela played the piano, this is shown in season 1 in a flashback where she is teaching Charlotte how to play. Red John likes the blind girl to play the piano too.

Reason 5. Red John says "Roll Tide" which is piece of orchestral music composed by Hans Zimmer.