AI discovering new zero-days isn't the real issue though.
AI's ability to seamlessly implement every single known vulnerability is the problem that can attack us at scale.
An AI trained on devices, software versions, and vulnerabilities could literally identify targets just by the hardware. It would passively identify and attack anything with out of date security software.
It's inevitable and we won't know it exists until one day some crazy number of the network routers in the world all stop working more or less at the same time.