There are already congestion charging schemes. I doubt it will ever get to a ban (and you can wouldn't want that) but I think it will be expensive. You could actually just charge a flat fee for road space, so a bus carrying 70 people is 3 times as long as a car, so only pays 3 times more. And maybe a separate charge of minimum standard to discourage nitrogen or particulate air pollution.

I suspect that the move to EV will eventually create a revenue hole from reduced fuel taxes necessitating the move to road pricing. Politically unpalatable but I think a necessary step.