Every single time that technology has made something massively more efficient, usage has gone significantly up, not down, as the efficiency enabled unexpected use cases.
The technology, here, is the algorithm and hardware related to self driving. Not the car itself. Yes, we will use self- navigating software and LIDARS for a lot of things (car, buses, trucks, planes, boats, shipping containers...). And we will find new uses for it too. But the car as an object will be considered an annoyance to have.
And probably heavily taxed to pay for roads, etc...