The question is, will we use them? Depends on how far in the future you are looking. Sure, maybe after hundreds of years there will be flying cars, and poop. They could be more environment-friendly, and you don't have to fix roads all the time. But for now, we shall stick to cars.
You're a little late.
Flying Car
The future is already here
1In hundreds of years the sun would be dying.
2On topic: There are already flying cars and as for your question of if it will ever be used by the general public, no because there would be mass pollution and there would be so much vehicles in the sky that it will be too cramped.
Have you thought about the money this will cost? Millions. If they made it cheap everyone would buy causing the world to get even more cramped. What if one breaks down? It will fall on a poor citizen.