"let alone a plan for how they would be safely operated in large numbers"
I think for that you're going to have to give up autonomy, for flying cars to be viable you can't trust people to pilot them, they will have to be machine controlled with a mixture of onboard (incase of network drop out) and centralised co-ordination to ensure flightpaths of vehicles stay clear of each other over the course of the trip.
So, we're going to be a bit away from that, plenty of time to actually figure out the flying vehicle bit....