I think this is more likely. Living in cities is desirable because you have a vibrant and 'close' community, it is undesirable because its hard to drive and if you do own a car its under utilized.
One of the interesting effects on this might be 'non-bus' cars. Which is to say public transit as a fleet of say 'four person' self driving cars where you walk to a bus top and touch your transit car and one shows up and picks you up. You tell it where you want to go and it takes you there.
It of course destroys the taxi business quite completely. But combines all manner of public transit into a single service which gets economies of scale. Dynamic electric cars would be fine (where they have an electric 'boom' like trains in Europe do).
Anything is possible, I just can't imagine a (US) municipality that's able to implement an entirely new public service. IIRC, community wi-fi keeps getting sued by companies that want to make money. First, none can afford it. Second the US, IMHO, is really hostile toward any sort of government service.
Even if those were non-issues, you still have to solve the problem of vandalism. People behave like grownups when other people are watching (pretty much). The bus or subway are good examples. Alone, in a car, i think it's much tougher to keep people well behaved. there have been various community bicycle programs that suffer from people beating the hell out of the bikes, or just stealing them.
These are perhaps mutable problems in small towns, or outside of the US.
Seattle has a light rail system they only booted up a few years ago. They had to build a completely new set of rails everywhere to do it. I'll admit I don't know the details of its history, since I wasn't paying attention, but it's utterly possible.
20 years is on the long side, but I find it a reasonable amount of time to make it happen. And the point was more that it happened, and that it wasn't exactly an isolated case.
