As per this article, the 12th Doctor will be revealed this coming sunday on BBC1 and on BBC america during the airing of "Doctor Who Live: The Next Doctor".
Very hyped to find out who it is. The article gives a strong possibility of who the next Doctor is!
I'm hoping it's not this Peter Capaldi guy the press seem to think it is. Granted I don't know anything about him, but having an older guy now after Tennant and Matt Smith just wouldn't feel right.