In an interview Xander said that he was honored to be chosen to play Red John, but that someone else deserved it.
And in the same interview Bruno said that he had chosen Thomas a year ago, after looking at everything and choosing him in the end.
Myself i like the idea of Thomas as Red John.
Sure i hoped it would be Bob or Michael Kirkland but i still like it.
Xander is such a good actor and i just hope that he will be known by this role.

Xander thank you for the amazing series, Bruno thanks for all the years you wasted in to the series to make us intrigued and enjoy it. I'm still gonna follow it even though i said i would stop after seeing Red John, but i'm still gonna follow it!