Alright, so we make this AI system that's way smarter than any human, and it can even make itself more intelligent over time.

Tell me- why would it kills us all? Certainly I can see an AI going "You know what? _insertGroup_ is a net negative for humanity and should be eliminated. Launching nukes now/creating specific virus/whatever."

But all of humanity? When it's supposedly more intelligent than us? Even if it has robots to keep the internet/electricity going I would think it would realize that it's going to get bored really quickly, not to mention we would effectively be its parents.

As far as other dangers, like it letting a rogue actor create some sort of supervirus, grey goo, or other superweapon: if it's intelligent enough to do that it'll probably be intelligent enough to quickly stop it.

Don't get me wrong; there's a risk. 50% though? Doubtful.