Stop making theories. Red John wasn't appeared in the show.
Red John and Patrick shake hands in the past, at the carnival or when Patrick is phychic.
Also Red Carpet1 posted the interview with Tom Szentgyorgyi:
"This season has been about Jane digging into the notion that it's not
that Red John could be anyone; it's that Red John is one of a very
specific set of people that Jane is uniquely qualified to investigate."
"The finale is going to pay that off in a way that will completely
change the hunt for Red John. We are going to know some very specific things about who he might be."
Otherwise: 5x22 Red John's Rules snippet:
It will feature a character called Sean Barlow who is an Irish psychic from Jane's past. He could become a recurring character.
