It's OVER !! .We were trying to discover who RED JOHN is the moment Lorelei Martins revealed a very big, game changing clue when she said Patrick and RED JOHN shook hands.

From that moment so many great theory and analysis from the fans were shown here in this great site,even if your theory or suspect didn't make it, that doesn't mean your theory is invalid ,Bruno Heller has to show one ending to it and if he could write multiple ending he would.
http://s21.postimg.org/q708c39yv/image.jpg

A BIG thank you to  Theory #12122 • By ozi  for the clearest clue to who RED JOHN is from the trailer.

And i would like to add that also the pigeon in the church from the trailer was a big clue too.

Didn't see that one coming