So apparently Moffat's quote about not making the episode a "fanfest" and "looking to the Future" is the official line for making it an 8th Anniversary Special.
I keep seeing comments like this and it is silly. Just because there aren't any returning Doctors from the classic series doesn't mean that the special won't celebrate all of the show's history. There are more ways to celebrate than having returning Doctors, or does fandom lack that kind of imagination?
"Canon is only important to certain people because they have to cling to their knowledge of the minutiae. Open your mind! Be a Star Trek fan and open your mind and say, 'Where does Star Trek want to take me now'." - Leonard Nimoy