Sorry, I'm late to this conversation so my apologies if someone has already mentioned what I say.
I think it's far more likely that the vehicles will have to be fully automated and controlled by some sort of, again, automated air traffic controller.
They could put in place some kind of flight corridors. I agree with both of you that some flight planning, clearance and point control are required pre-implementation.
Google is already testing self-driving cars around London (with a real driver in place should there be an emergency.) One did have a crash, but there is bound to be teething problems. Amazon and Microsoft also want to get in on the act. Self-driving cars are meant to considerably reduce the chances of accidents. Most new cars already have those parking detectors. I can't see a huge leap between self-driving ground cars and self-driving air cars in the software required. I appreciate there is more chance of catastrophic accidents because there is no option to simply break and stand still.
The problem for a flying vehicle is, therefore, the complete lack of anywhere from which to take off and on which to land. The main road runs up a hill. From part way down the hill, it looks as if the trees form a tunnel; they don't (the trees on either side don't touch), but it's very picturesque.
The most dangerous part of any kind of flight (aircraft, ballooning, parachuting) is the take off and the landing. Taking off and landing on a street has particular hazards - not just the street trees, but lamp-posts, telegraph poles, signs and flags, radio masts and all the other street furniture. I think this will be the biggest problem.
Driving a flying car will need a special licence, so in my mind those idiots will never pass the exam.
I think that's why they will need to be fully automated and self-driving. There are driving tests now, but it doesn't stop idiots (including kids as young as four) driving miniature motorbikes and quad-bikes in parks, along pavements and cycle-ways.
The cost has been mentioned. The cost will be reduced by mass-production as is always the case. Cars were once only for the Uber-rich. TVs, washing machines and mobile phones were also once beyond the affordability of someone on the average wage.
The environmental cost has been mentioned. Well, since we are all going to Hell in a hand cart anyway because we are doing nothing about man-made CO² lets all go out with a bang! Wouldn't these be electric though? And in the 1950's they were all going to be atomic powered!
It would be nice to think that computers and the internet are going to allow us all to work from home too - so no need to travel at all, but they fact is that most jobs will be done by robots in any case (if they aren't already.) The jobs that will remain will be in the creative arts, in catering, teaching and caring professions - so cooks and chefs, doctors and nurses, teachers and lecturers, trainers and care assistants - who will all still need to travel to their place of work. Maybe the artists, writers and designers will have the luxury of staying and working from home but few others will.
Also, what about journeys for leisure? And going on vacation?
Weirdly enough through I could see flat roofed housing booms. Gotta park your gyrocopter somewhere.
Well, green roofs are going to become more popular, so why not park it on your rooftop lawn?
However, the only way we will build enough houses for our out of control population is to build high-rise blocks. Those mega-cities won't have the option of rooftop parking so I'm not sure that will work. Didn't cartoon family,
The Jetsons, fly in through their window?