Of course, this all comes apart when you remember that the Twelfth Doctor (what little we've heard from him so far) speaks with Capaldi's natural Scottish accent, very different from Hartnell's clipped BBC received pronunciation. But that could be a side-effect of hallucinating Amy Pond moments before the regeneration completed. In a line cut from 'The Christmas Invasion', the Tenth Doctor's change of accent from Nine's northern was to have been explained by the presence of Rose. I doubt this explanation will ever be explicitly included in the show, but if Capaldi's Doctor is to have parallels with the original then I think this could stand up as an implied explanation. After Steven Moffat has bowed out as showrunner, 'Doctor Who' continuity will take whatever course his replacement deems fit and it's unlikely that we'll see Capaldi's successor pop up as a recorder-playing cosmic hobo. But head canon has been known to bleed over sometimes. This is just a fan-theory, one that will most likely be disproven rather effectively as we eke out more details on the new Doctor and invalidated entirely once series eight hits our screens later this year. But in the meantime, we can speculate (as us fanboys are wont to do) and I think there's enough evidence out there to give it some consideration.
