I don't really think Rigsby is Red John.  However, it was weird that Rigsby told Cho that he was going to fix him up with a girl.  Then the female dectective shows up and starts coming on to Cho.  Rigsby could not have murdered her because he was at HQ as her murder was in progress.  Is this just a coincidental or maybe evidence of some unapparent connection?  Perhaps the writers are just toying with us.  Maybe Rigsby or Cho has three dots tattooed on his left shoulder. 

The suspence builds!