"Recognize that BMW/Daimler/et al really don't want true self driving cars. It's not really in their interest, because it would radically reduce the need for car ownership and would open up a new world of on-the-fly car rental."

This is exactly what is happening, without self-driving cars. E.g. Drive Now is a very popular service in several german cities, and one of the reasons why I don't feel the need to own a car while living in Berlin. I can just hop in a car any time I like, drive around, and then park it anywhere in the city.