The odds of computers becoming thoughtful enough to decide they want to take over the world, hatch a nefarious plan to do so, and then execute said plan remain exquisitely small. Yes, it’s in the realm of the possible. No, it’s not in the realm of the probable. If you want to worry about existential threats, I would suggest that the old-school Biblical ones — flood, famine, pestilence, plague, war — are still the best place to set your sights.