The most interesting part of the whole rumour to me has been the suggestion that he's filling the function in the story that Eccleston would have if had agreed to appear. Add that to Rose's post-Apocalyptic outfit and it does raise some interesting possibilities that may tie in with the suposed Series Finale synopsis that has appeared.
Piggy backing off that.
Why haven't we seen any alternate universe doctors?
What if there was a doctor in Pete's World who still went back to Galifrey on a regular basis etc?
Is the doctor excluded from the multi universe concept?