If Stiles is really dead, I can't see Red John being one of any of the other seven suspects; Heller compared, regularly, Jane to Sherlock Holmes and Red John to Moriarty. 
Both Bertram and Smith are in on it, that much is obvious, but Red John? Heller's representation of the ultimate good is Patrick Jane, in that the death of his family caused him to see the world with abnormal clarity; Red John is not, as many suppose, Jane's polar opposite, but rather someone just as clever and charismatic, just driven (possibly even by similar motives) to a different end, that of evil.
Red John would not hide this charisma and intelligence as Heller would have us believe Bertram or Smith do. He would glorify in it, rather like Bret Stiles, and would take pleasure from mental jousting with Jane. However, Stiles is dead, and even if he weren't, I'm not so sure that he is Red John. Someone linked to Visualize, but who has a similar history as Jane in the Carny industry would be the ultimate Red John in my opinion. Red John is still pulling the strings, somewhere, watching Jane and laughing at him.  
But all will be revealed in episode eight, I suppose... just please do your brilliant story justice Heller, and make RJ the Moriarty we've all been hoping for.