I am very angry beacuse some of here so silly.

"The cards are up on the table and they're the real cards," Heller tells
TVGuide.com. "There is no sort of double twist. There's no more messing
around. We've been through all the twists and turns of plot, and we're
now getting to the truth. Only the truth gets revealed from now on in."

So, one of them (7 suspects) is the real Red John! There isn't trick. And he also said before Patrick Jane isn't Red John!!!!! Despite of there are more than 100 theory about Patrick Jane!!!! It's a shame!!

My opinion is, Brett Partridge or Gale Bertram is Red John. If the handshaking was true and we saw it, obviusly Gale Bertram is the nemezis serial killer.

But, my first guess is since end of the season 2: Brett Partrige is Red John.

I'am fine because:

"This is the final chase," Heller says. "We will know who Red John is
and we will catch him next season. Everything that has happened over
ther past five years will come to a head, and things will change
drastically. This is the biggest finale in terms of game-changing and
setting up for the last act of the Red John saga. This is as definitive
and revolutionary as you can get."