The new issue of Doctor Who Magazine (#460) which is released tomorrow reveals that David Tennant is the only past Doctor who will be appearing in the 50th Anniversary Special.
The magazine also confirms that Christopher Eccleston was approached to take part, but he will not be appearing.
Show boss Steven Moffat says of the special episode that will see David Tennant and Matt Smith join forces "We can't make this all about looking backward..."
Other cast confirmed for the episode include Jenna-Louise Coleman, Billie Piper, Joanna Page and John Hurt.
Thanks to Steve Ryder.