The fundamental problem with autonomous vehicles is that I haven't seen (and can't think of) a gradual rollout plan. As it stands, the idea seems to be, as soon as the AI is good enough, autonomous cars will flood the streets. But in the mean time, zero.

Well, that's not going to work, and not just for technical reasons.

That reminds me of IPv6. There is no technical challenge to implementing it, but we're still running out of IPv4 addresses, simply because the designers had no plan for gradual adoption. (Dual stacks was not such a plan, in fact dual stacks was an effective way of delaying adoption compared to any other design choice.)

People (users, insurers, legislators, regulators, lenders, investors ...) won't be confident with autonomous cars if they have no practical experience to look at to trust them. And maybe they will, but at the first significant / publicized accidents, they will be demonized, banned or penalized.