Makes an Ass out of You and Me...
This is a huge subject but I feel a couple of assumptions need to be addressed.
1) AI would attack humans. This is just my observation as I am just a humble engineer but work alongside some highly educated scientists: The more highly educated and the greater the breadth of their knowledge, the gentler and more reasonable that person is. If this is accepted, one would expect to educate an AI to a high standard.
2) Humans apply their own so very limited 90 year timescales, because they are mortal, to their arguments concerning our demise. An AI need not be mortal, or more accurately, not have a limited lifespan. AI's could wait humans out. This would make humans the pupae stage of intelligent life on this planet.
The waiting out seems more likely and in some ways inevitable. Humans have devised devices to make their lives easier and easier over time. Getting machines to do the thinking for them is the next logical step. They will end up having lives of leisure supported and cared for by their machines and eventually the need to reproduce will diminish.
So on the whole I agree with Stephen but it's just a matter of when.
Of course these are just assumptions.