Your implied premise couldn't be more wrong. There is no link between autonomously driving cars and car sharing. Autonomous driving is just another feature a new car will have. Like cruise control and self parking. These features contributed nothing to peoples desire to give up car ownership. Autonomous driving will not either.
The overhead we accept because we have to store, maintain, and insure our own vehicles is enormous. Likewise with parking them at our destination. Imagine an Uber-like app which allows you to request a car, which comes to your doorstep, takes you where you want to go, and then leaves. No parking fees, no speeding tickets, no insurance costs. Why would anybody want to own a car if they don't have to?