Not a guess about Red John, but some observations:

1.  Why did Cho come in from outside the diner several minutes after Van Pelt , Rigsby, and Jane.  This is very suspicious to me. I would hate for Cho to be involved with Red John, but this really struck me as odd behavior,

2.  That is the first time I've really noticed CBI Ron talking in the show.  Who was he on his cell phone with?