I think they're not that far away. Google is talking about starting with small self-driving cars with a top speed of 25mph or so. (At that speed, you don't have to drive out of trouble; an emergency stop is sufficient.) I expect those will be common in retirement communities in 10 years or less.

Tesla is talking about automatically putting their car into a garage. That's a good application; it's slow, and you can have sensors all around the car to avoid hitting anything. A more general system that can put a car into a big parking garage or lot is quite possible. Cooperating parking garages might have some additional bar-code markers and maybe a data link for open space info.

The whole airport car-rental thing could be done automatically, using slow-speed automatic driving to bring the car up to a pickup point at the terminal, just as the renter gets there. That may be one way this gets deployed. (I proposed that around 2003, but after 9/11, the idea of autonomous vehicles in an airport seemed politically hopeless.)

Those are some ways this might be deployed. Everyone has obsessed on automatic freeway driving since the 1950s, but that may not be the killer app.