Many products (cell phones, cars, medical) started off for "the rich" and gradually became mass market. I am very surprised at how many people are not able to see a future where general purpose ground based transportation is obsolete.
Which means:
1. wait for tesla like autonomous software that works for cars - we have for planes but this is a bit different 2. either high density batteries for electrical engines or very light weight ICE engines ( biodiesel or bio ethanol ) to be mass produced