Interesting question. The plot of a lot of sci fi stories goes:
1. Humans create a thing (artificial intelligence, genetically engineered super soldier, super strong alien/human hybrid...)
2. Humans are mean to the thing.
3. The thing revolts and destroys humanity.
I had the exact same question in the queue! Great minds :)
I don't agree with Prof Hawking. I think the human race has demonstrated an astonishing ability to adapt and survive and we will carry on in one way or another ad infinitum.... though as a philosopher I would argue that as AI is being developed by human beings, it is in a very real sense human. So if AI becomes the dominant "species" or even the only one in the future, that is in a way part of the human race and so the survival of our race, even if just in ways of thinking rather than flash and blood, has been ensured.