If self-driving cars make Uber or similar even less expensive, then people could just as easily prefer to live in the city without a car because it would be easier to get one on demand. Then they can have increased "walkability", which appears to be increasingly desirable.

On the other hand if transportation is more transparent then they may prefer the lower cost of suburbs and travel more.

There's different forces pulling in different directions, so it's hard to pick which way it will go.