Another side of this "Valeyard" coin is that Doctor Hurt could be a manifestation of the darker parts of the Doctor's personality. The parts that allow him to kill when needed, or otherwise be nasty to his enemies. We have seen this side quite a bit in the last few seasons, in both Doctor 10 and Doctor 11 stories. We tend to find that the more the Doctor goes without a companion, the more isolated and apt to do "darker" things he gets. This could be Doctor Hurt. Likelihood? Not likely. This really is a "been there, done that" theory. We even had an episode with a very similar character in Season 5 with "Amy's Choice" and the wonderful Toby Jones as the Dream Lord. I can't see them pulling this one out again so soon when there are so many other directions to go with the character.