Dave unless and until anything of this ilk can be automated with multiple fail-safes, I don't see it happening. Initially cars were tough to start, stop, and steer and roads were dirt tracks. Only a few were capable of even starting the old T's and the 1:1 steering was a bear to control. Thus a small market. In order to sell more vehicles and attract the less capable, manufactures made vehicles easier to start (electric starting), stop, steer (power), enclosed bodies with heat and air-conditioning, entertainment systems (cause getting there alive isn't enough to prevent boredom). Not enough: well we now have vehicles that park themselves (God knows how difficult it is to back AND make two turns); vehicles that look back and to the side (very difficult to TURN your head before pulling out or to look BEHIND you before backing); Keyless locks and ignition (gomer can't remember where he put the keys an hour ago), AND vehicles that stop themselves (heck, you really don't expect me to continually look FORWARD, too, do you). Heck, if you can wipe the drool off your chin you too can have 2000lbs of steel going down the road at 70mph. Thus:
In 2014, 32,719 people died in car accidents. These are what you want zooming around in another dimension?
Look at small aircraft the "general aviation" category. There are multiple regulations controlling pilots and aircraft maintenance in addition to a nation-wide control and tracking system yet in 2014, while no one died on a US commercial carrier, 252 died in small, privately owned aircraft. Doesn't sound like very many compared to cars, but consider that in 2013 there were roughly 200,000 General Aviation craft to 256,000,000 registered vehicles, 185,000,000 of them passenger cars. Roughly 925 more cars than planes. Applying that data to these drones we'd expect that with auto drivers zooming around in the 3rd dimension with their drones we'd expect to see 233,100 deaths from crashes.