Flying cars are actually *really* hard, and require a energy revolution before they become possible except maybe for the super-rich, and would probably require high level computing to make it easier then piloting a plane.
People have tried very hard, but its simply not doable with our current tech level, and will probably never be possible (well unless we have a technological singularity or something). Personal helicopters maybe, but everyone having flying cars is very unlikely.
Here is the Parajet Skycar
They cost £55,000 and the company is accepting orders now
It is considered a powered parachute / ultralight, and requires a relevant license that typically takes 1-2 weeks to get.
Here is the Terrafugia Fusion
Purchase price is $279,000
First shipments are expected this year
You do however, have to have at least a Sport Pilot's license to fly one legally.
Here is the Pal-V One three-wheel roadable gyrocopter
It is, unfortunately, still in development with no scheduled date of commercial availability, but is estimated to become available for $300,000.
It can be done. It has been done. At one time, automobiles and cell phones were toys for the rich, too. You might start seeing these things on the road and in the air within a year or two. In 5-10 years they might be common.
These aren't flying cars.
One is a glider, and you can't just switch between flying and on the ground without taking off the parachute first. the other is a plane that also has limited car abilities that would be a menace on a road. and one is a helicopter/car, that probably wouldn't work very well as a car either.
They are basically already workable aviation methods that have cars strapped on to them.
Furthermore, these wouldn't work at a large scale, fuel is a concern, as well as the problems with accidents (avoidable to some extent with computer systems, but as long as you are giving the drivers any control, they *will* end up crashing them sometimes, and considerably more then cars crash today). There is a reason that pilots licenses are so much harder to get then car licenses, and having flying cars would only cause a whole lot of problems in that regard.
I don't think the traffic problem with a million of these flying about new york city would be easy either, and unless they were restricted to pre-controlled lanes or entirely controlled by computers, would result in a lot of crashes.
It would also be a nightmare with security (it would be extremely easy to get a flying car loaded with bombs and fly it into the whitehouse, or over the border, or into a generic building), and I know the big governments would have some real problems with them even if they did become suddenly easily accessible and cheap.
EDIT: The flying helicopter one looks pretty road accessible though.
But they are all expensive (except the first one, which is basically a car glider), and aren't affordable unless you are pretty much a millionaire.