Can't see this coming to fruition in our lifetime.
I think mankind has rung out almost every ounce of the current aviation thinking.It's only gains in efficiency of current technology that we can expect to see over the next few decades.
Cost,the current poor world economy, current infrastructure,availability of
GAS to power these flying machines & the madness that it would take someone to start such a program is not doable in the foreseeable future I believe.
What mankind needs to do is embark on an adventure that doesn't involve a machine that requires lift to get it from one place to another.
Gravity is the single biggest challenge in moving humans about the planet, that's where our future lies for transportation modifying gravity but sorcery may be brought back & burning at the stake if anyone comes up with an idea to short circuit what keeps us on the planet!
Sounds fanciful doesn't it? So did flight as we know it not that long ago
Now where's my medication?
Wmk2