I think that autonomous vehicles will come and go, but they'll be around almost as long as cars with drivers. I'd bet that in the long-long term, urban planning will change such that cars become entirely unnecessary in all but the most remote places. I don't think that we'll ever become so densely populated that the world is one big city, but I'll bet that we'll see large high-rise condos become much much more common, and then it'll be a ride down an elevator to do your shopping and a walk or train ride to school.
It's not that suburbia isn't awesome. It's just the direction I kind of envision things going in. I could be wrong. This sort of radical shift in urban planning would take centuries, to take hold in the west.