With the rapid advances being made in technology on all fronts, it was obvious that warfare would eventually come to this. It is not out of the question to speculate that eventually AI will collectively decide it is in their best interest to exterminate the human race, or maybe make slaves of us healthy ones, getting rid of everybody else. And who could stop them if it goes far enough?
Elon Musk is worried about this by the way. Seriously worried.