This is not a theory about who Red John is, but who he is not.  I think that both Jane and Red John left one person off of their lists on purpose.  This will be the twist that will be needed (because they need one).  I think each of the five remaining suspects may be involved and certainly four of them are (Bertram Haffner McCallister and Smith). 
I really have no idea who the last person will be, but we know them, they have been on multiple episodes before otherwise it would be anti-climactic to see who the person is.  I suspect that the drama will more fully unfold in the breakdown of the secret society run by Red John and how he stayed informed of all of Jane's activities.