I just read Theory #3123. The author speaks about the ring Red John is wearing on his left hand. Betram is the only one wearing a ring. It was like a revelation to me. Red John is not a single person. I think this Red John who is wearing a ring is Bertram but I don't think that Bertram is the only Red John. There are many Red Johns. 
It seems possible for all the seven people on the list to be Red John (or maybe just some of them).
I think Red John is like the demon from the Bible; when Jesus asked him his name, he replied: "My name is legion for we are many". 
I think Red John is not a person, but a title, a distinction. And I will go further and say that the Red John's accomplices who got caught are people who didn't pass the initiation test for becoming a red john.
(I have to mention that the religious analogy is just for the analogy's sake)