As much as I don't want the show to end, I think that there was quite a bit of evidence in that episode that 11 (or at least who we think is 11 at the moment, but I'm not going to get into the whole John Hurt business), is the Last Doctor.

1. The dead TARDIS being used as a tomb was clearly the current console room, which suggests the Doctor will die before it changes again. Of course, you could argue that they just used it for convinience, as it's what we currently recognize as the TARDIS, and that it can change, but will change back before he dies. However:

2. The window on the massive TARDIS had the same crack that the smaller TARDIS sustained in this episode. The deliberately showed us the crack, which seemed to serve no particular purpose, and it was definitely a concious decision to include it in the big TARDIS, so Moffat is trying to tell us something. The Doctor loves his TARDIS, so I see no reason why he would leave the crack in the window for very long, meaning the point when he dies can't be far off.

3. We were promised in 'Lets Kill Hitler' that the Question would be asked at the 'Fall of the Eleventh'. Maybe this did not refer to the time at which Eleven died, but it was telling us that the question would be asked at the exact place where the 'Fall of the Eleventh' had previously occured, on Trenzalore, exactly where his grave would be. Basically, I'm suggesting that in the phrase, "On the fields of Trenzalore, at the Fall of the Eleventh, a Question will be asked", the 'Fall of the Eleventh is not referring to the Temporal location of the question being asked, but further clarifying exactly where on Trenzalore it will be asked; right outside the Doctors Tomb, as we saw last night. This suggests that the Doctor who dies in the 'small battle' on Trenzalore is in fact the Eleventh Doctor, and there are no more after him.

4. Clara was spread out into the Doctor's entire past and future, and she clearly said in the final scene that she had seen all Eleven incarnations of the Doctor. If there were to be any more, she would of course have seen them, but she didn't, so Eleven must be the last.

I'm not by any means saying that this is definitive proof, but it seems to be quite a bit of evidence all pointing in the same direction.

The introduction of John Hurts character could interfere with this theory, but given we have no idea where he fits into the timestream, we don't really know if his character contradicts the theory. If he's a future Doctor, maybe Trenzalore is the place where the person named the Doctor dies, as in he no-longer calls himself that, but the actual person lives on under a different name, as John Hurt. If he is a past Doctor, it doesn't seem to contradict my theory.

What do people think?

I certainly find it odd how Clara only saw 11 Doctors, plus the John Hurt one. Like you said, if the Doctor died say at the end of his 13th Regeneration, she should have seen 13 faces. A very weak explanation would be that, as she was entering the Time Line from the time of the 11th Doctor, she could only go backwards to save him, not forwards.

I doubt the 11th is the last though. I mean, they're not cancelling the show. And if they are going to make series 8 all about the Doctor avoiding his death on Trenzalore.... didn't they kind of do that storyline in series 6? It looks to me like Trenzalore will become an unspoken ending to the series for the future. We know the Doctor will end up there but we do not know when. If the day comes, and it will do, that the show ends, and they do not get to show the death of the Doctor, we can just assume that, eventually, he dies on Trenzalore.

Maybe Clara saved the Doc at the wrong moment- when he was supposed to have regenerated? This could possibly lead to the creation of another Doctor, or allow one to grow older that he had originally?

Probably not, but just an idea that occrred.

Well time can be rewritten, so it could be that as it stands the Eleventh is the last, but then he manages to change his own future. That would kind of fly in the face of TATM though, as he has seen his own grave. It does seem likely though that I'm thinking into it that much, and it's just meant to show that eventually the Doctor will die on Trenzalore, but it won't happen for a long time.

Because at the point in time The Doctor was dying and would have died as The GI went in to his Time Stream and changed everything so there was no future Doctors any more.

At the point Clara stepped into the Time Stream there wouldn't have been any future Doctors or TARDIS's for her to see until she put things right.