Once the first ones are available on the open market, I'd expect at least 10 years of them being very expensive rich peoples' toys while the remaining edge cases and kinks in the tech are worked out, manufacturing scales up, insurance and legal issues get sorted out, various road maintenance departments learn to deal with their needs, etc.
It's possible that such vehicles will have 5x-10x total occupancy per day of regular vehicles(which sit idle at most times). And it could imagine how the right financial incentives would shift a large share of the manufacturing capacity towards such cars. And considering the car replacement rate at probably something like 20 years - maybe 10 years is a possibility of starting to have that conversation.
I could believe that the first generation of fully automated cars might be available for purchase in ten years.
Cars sit idle 95% of the time. That means you only need to flip 5-10% of the total fleet. Tesla could do it by themselves building 2-4 million cars/year, with the amount of cars needed per year declining the higher the utilization level you can achieve.
Disincentivize rush hour using congestion pricing.
40K people a year die in the US from vehicle accidents. Why would you not ban humans from driving if machines were objectively superior? Where do you find the "right" to drive to be? Driving is a privilege granted by the government, not a right.
If fully-automated vehicles become commercially available (which seems likely at some point, though not in the immediate future), we will likely see rapid adoption in the applications where they are very well suited, followed by a long, slow, gradual trend toward broader usage. The hardest cases will be the ones sticking around longest, and one can't simply legislate them out of existence. Just replacing a small percentage of the fleet won't come anywhere close! It's only when automated cars have become so dominant that only a small percentage of the fleet still depends on manual drivers that it will become practical to start talking about a ban on manual operation.
To be there I do think we need the first generation of fully automated cars available to the general public in 5 years or less, which I think we're actually close to or we wouldn't be having this very discussion...
Self-driving, electric cars will make future taxi-equivalents affordable enough that it's considered for many instances. That makes for a massive market.
It's not as though current taxis have a sparkling reputation as drivers either. Not many will be sad to see the end of them.