due to people sharing, etc.
My layman prediction is that what are currently auto insurance firms will become auto membership clubs. It works like this:
1) Most people don't need to actually own a car, they just have their daily commute, shopping, and incidentals
2) If someone doesn't need to use their car while they're working or sleeping, they can rent it out for others to use (Uber => UberMech, which matches need to capacity minus the driver)
3) If someone is satisfied renting the cars of others, they likely won't own one at all (all but guaranteed for those who live in large cities, many of whom just rely on taxis for the moment)
Insurance companies will want to get in on renting out the vehicle, one part extra cash and one part liability concerns. They offer to manage renting out a member's car to other members needing extra capacity (eg. a larger family who only has one or two vehicles) to get the member some extra cash (the company's cut covers profit+extra liability). Eventually, most of their customers will only use them for the car-usage service, and as private ownership drops away the insurance companies start buying and maintaining their own fleet, perhaps outright purchasing existing car rental companies (who have been undergoing similar transformations during this time). "Micro-term" auto rentals (that is, use of a vehicle for under an hour at a time, likely 20 minutes a time) become the mainstay of the company and insurance is a minor product they offer for the minority of people who desire personal vehicles.
As automatic buses become standard, bus routes will increase because smaller, driver-less buses will have better access to residential areas. (They could act as track-less trollies, perhaps not even stopping completely in some areas and just having a long on/off zone at 5 MPH.) This will further drive down private ownership, but people will still like the idea of having a vehicle available for their convenience.