My theory is that Hurt is the 8th Doctor. This would also explain why McGann is excluded from the 50th, even though he has always been overly desperate to continue his role as The Doctor in some way or another. If they wanted McGann in the 50th, they had him.
I know there are a lot of eighth Doctor fans around, and there have been many books and audio dramas continuing the eighth Doctor's story... But let's face it, the eighth Doctor was a huge misstep. It was a really, really, really, really, really shitty made for TV 90's movie that didn't even bother to follow established Who continuity (stating that he is part human, and some other departures from established lore). They also portrayed The Doctor as a bit of a buffoon, showing him puzzled by earthly things and habbits, I guess to drive home the point that he was an alien to American audiences. The whole thing was absolutely awful. I think the reason why eighth Doctor stuff is kind of popular is because it was a whole wasted regeneration of the Doctor, wide open blank pages, just about anything could be done during it, so why not capitalize on that with novels, comics, and audio dramas? But that stuff isn't canonical. Is the crappy made for TV movie even canon? I mean, we see McGann's face flashed on the screen in a couple of Smith's episodes when they are trying to remind us of old Doctors, in the first Smith episode, and that last one with all the flashback bits. So yeah, it is established that McGann was the 8th, but is anything we know that was done by the 8th solid continuity? The movie can't be, because it is contradictory (and just plain sucked, even by RTD era standards), and the books are essentially expanded universe.
So, my theory is that time locking of the Timelords and the Daleks and all the things that happened that gave 9 and 10 their brooding survivor's guilt ridden aspects were done by the 8th, and John Hurt is McGann all grown up. The 8th Doctor, as far as the TV show is concerned, is still a bunch of blank pages they can do anything with.
It fits with everything we know, and explains the exclusion of McGann*. He was a previous Doctor who rejected the title Doctor and did some pretty terrible things, which he says he had no choice in. Time War, awful things, eventually regenerating into brooding Eccleston who got back on track as the Doctor, but still had to live with the stuff done by 8.
*Of course, the exclusion of McGann could also be explained by that movie being so absolutely terrible that nobody wants to have to be reminded of it. Even the worst bits of Doctor Who since its 2005 revival are significantly less difficult to watch than the entirety of that atrocity of a "film".