In the new issue of Radio Times, out in the UK today, a brief comment in the Grapevine column suggests strongly that one of the living classic Doctors will be in the anniversary special.
‘We hear from a reliable source,’ the magazine claims, clarifying that ‘we’re pretty sure that Colin Baker, Paul McGann, Tom Baker, Sylvester McCoy or Peter Davison will make an appearance.’
The column also suggests that the ‘identity of the new Doctor’ will be announced in August, and that ‘serious consideration is being given to unveiling him (or her) on a surprise Doctor Who Confidential as happened with Matt Smith’s unveiling in 2010.’ (actually 2009!)
Sci-Fi Bulletin: Exploring the Universes of SF, Fantasy, Horror and Spy-fi! 
Got to be mcgann considering the hurt development….
It would make some degree of sense…
yeah, how would they explain an OLD version of a Doctor that regenerated well before they aged to that extent…
McGann would seem to be the logical choice on that basis wouldn’t he…?
The beauty of Doctor Who is that nothing needs to make logical sense. I can imagine Tom Baker popping up and say ‘would you like a jelly baby? Sorry, they are a bit squashed by time, like me!!’
I imagine it will be flashback photos/audio/footage of them as we’ve seen a lot recently in Moffat era Who…