Check out FutureCars.com. They provide a fairly comprehensive overview of future automobile technologies with an emphasis on future fuels. Plus, they provide a good run-down on the various ways that the flying car scenario might be realized, including this summary of the challenges that need to be overcome:
A flying car should:
be able to utilize the current infrastructures for both cars and airplanes
feature a flight system that does not require the owner to have a pilot’s license
meet all FAA regulations
be fuel efficient and economically viable for the average car buyer
be powered by renewable fuels

That’s a pretty good summary. I would venture to guess that we will solve our energy problems and have some fairly sophisticated AI in place before we see a true flying car. A machine that flies but that requires no more highly developed skills than those required to operate an automboile is going to have to be highly automated.