I am unsure of the timing. I can describe the "road" map :-p
And, i am not sure i would call them flying cars. More like, cars that don't fall.
But, it is not long after that, to make flying... so

It is also not so much these technologies are held back from us,
it is that the entire university science is wrong. We've been led down the wrong path.
When we are back on the correct path, these inventions are pretty much obvious.