50th Anniversary Special

Okay, so there's a common them among the 10th, 20th, & 30th anniversary specials: they all have been multi–Doctor episodes that featured a Time Lord/Lady as the villain. First we had The Three Doctors with Omega, then we had The Five Doctors with Borusa, and then we had Dimensions in Time with the Rani. Moffatt had better darn well keep this tradition up, and have the Doctor team up with his other selves to go against some Time Lord for the 50th Anniversary Special. The Master seems like a bit too obvious a choice for this, I would actually prefer that the Doctor go up against the Valeyard.