> I could easily see them offering driverless cars only as-a-service.
They do this now; it's called "leasing". But if they're going to stop selling cars and only lease them, why wait? It's a bookkeeping detail that's unrelated to the car itself.
Cars depreciate in value so heavily, I don't know why auto manufacturers would want to adopt 100% of that loss—but there isn't anything currently stopping them.