Scanning the new Doctor Who annual (woo-hoo!), in a background article regarding the Time War, and written by Russell T Davies :
And far away, across the universe, on the planet Crafe Tec Heydra, one side of a mountain carries carvings and hieroglyphs, crude representations of an invisible War. The artwork shows two races clashing, one metal, one flesh; a fearsome explosion; and a solitary survivor walking away from the wreckage. Solitary? Perhaps not. Under this figure, a phrase has been scratched in the stone, which translates as: you are not alone.
Jon Pertwee usually faced the Delgardo Master.
Peter Davison usually faced the Ainley Master.
Production members have indicated that Anthony Stewart Head will be appearing in the Episode School Reunion as the Headmaster.
Call me incredibly suspicious here.
By the way, School Reunion has been confirmed to have both Sarah Jane Smith and K-9 in it. Captain Jack, unfortunately, won't be back until the third season.
And let's not forget Torchwood - this year's Bad Wolf. Interestingly, it's not only an anagram for Doctor Who, but the BBC have registered a torchwood web address. And best of all? It's already appeared in season one - as the answer to one of the questions on the Weakest Link.
Let the speculation begin....