> Superintelligence poses an existential threat to humanity

I disagree at least on this one. I don't see any scenario where superintelligence comes into existence, but is for some reason limited to a mediocrity that puts it in contention with humans. That equilibrium is very narrow, and there's no good reason to believe machine-intelligence would settle there. It's a vanishingly low chance event. It considerably changes the later 1-in-n part of your comment.