This show has been going forever, but seems to have boxed itself in to a conclusion. We already know two things:
ONE is that Dr Who dies when he is 1100 years old – and does not regenerate. He is played by Matt Smith – so that indicates Smith is the last person who will play the Dr.
TWO is that the person who kills him is probably River Song – who died and was saved in the library computer … before the Dr. is killed.
We therefore have an interesting temporal structure developing. We also need to discover who actually kills WHO …