Banning all other traffic is of course a solution, but it is hugely unpopular for obvious reasons, so I doubt it will pass.

It will happen slowly, through raising the price of individual vehicles (you can already see the trend with electric vehicles - there are almost no affordable sub $30k cars), raising the price of insuring a human-driven vehicle, etc.

It won't happen overnight, and probably take anywhere between 30-50 years, but it's definitely possible in the long term.

The problem with that theory is that auto manufacturers face declining average costs and so are incentivized to produce more cars and sell them for a lower unit price.

This is why the only source of auto inflation is by adding more features to the car. I don't see any reason why this would change in the future.

For EVs, wait until cheap Chinese EVs flood the US market.

That sounds like it would further increase car dependence in city's, how you see city's improving in this scenario?

oh I'm absolutely not saying this is a good idea. But what I am saying is that it could become politically feasible if tons of money gets poured into self-driving vehicles and they slowly chip away at "open" use of public streets.

Look at what the automobile industry did with "jaywalking" and removal of street cars.