That's why I said displacing walking won't happen.
You can fantasize a sci-fi future where people have real hoverboards that self-drive so you can just stand on them while they whisk you along. Forget the tech, just assume it's possible that these things could take up no more room than the toys we're currently calling hoverboards. Who's going to pay to give them to everyone? Because if you don't, the slow walkers are going to get in the way of the floaters.
When cars replaced carriages, those who couldn't afford them eventually moved to the sidewalks. Take over the sidewalks and where to the poor folks go?