I cannot say who Red John is at this point, but I don't think Brett Stiles is Red John.  The reason is that the rivalry between BS and PJ is too obvious, not to mention how SIMILAR they are.  Both men have a "cult" like following, are highly charismatic and know how to work people -- of course, they'd be uneasy toward one another, they cannot influence each other!!  For now, it is a sore spot, but someday, I predict it will turn into something almost resembling mutual respect, and they will possibly work together to get Red John. 

ONE thing I know for CERTAIN:  neither PJ or BS are RJ -- because RJ is a power hungry sociopath incapable of caring about others.  Both BS and PJ deep care for others, no matter how much they play it off.

RJ probably has an ordinary, mundane life,"invisible" because of a seeming respectable or meek quality, or he is in an enviable position as a sort of prodigal son, in a family of wealth, power and influence where he is always in the shadow of a more power person within his family.  No doubt, RJ feels "robbed" and wants to achieve the glory that both Stiles and Jane enjoy daily and experience effortlessly, but that EJ secretly fears he's incapable of [which is true!].  RJ wants to be like PJ and BS, and deeply admires both.  He's someone who has likely positioned himself very closely to both men.  LOVE THIS SHOW!!