A few years back Bill Joy was sounding the alarm on nanotechnology. He sounded a lot like Elon Musk does today. Nanobots could be a run-away technology that would reduce the world to "grey goo". But nothing like that will ever happen. The world is already awash in nanobots. We call them bacteria. Given the right conditions, they grow at an exponential rate. But they don't consume the entire earth in a couple of days, because "the right conditions" can't be sustained. They run out of energy. They drown in their own waste.
AI will be the same. Yes, machines are better than us at some things, and that list is growing all the time. But biology is ferociously good at converting sunlight into pockets of low entropy. AI such as it exists today is terrible at dealing with the physical world, and only through a tremendous amount of effort are we able to keep it running. If the machines turn on us, we can just stop repairing them.