Autonomy subscriptions are how things are going to go, I called this a long time ago. It makes too much sense in terms of continuous development and operations/support to not have a subscription -- and subscriptions will likely double as insurance at some point in the future (once the car is driving itself 100% of the time, and liability is always with the self driving stack anyway). Of course, people won't like this…
At least in cities, a fully-functioning, on-demand autonomous fleet would probably be superior to car ownership in just about every way except as a status symbol.