The inexerable loss of power from vectored thrust will be a hurdle for decades to come for them. To vector thrust like a Harrier requires about 1000 times more horsepower to lift a pound of payload. This penalty is fine when you need a military aircraft to bomb the end of its own runway, but it is almost laughable for any vehicle that must earn its way. It is elegant, in its way, but of no practicality in the real commercial world.
Those who don't understand disk loading are doomed to chase the sexiest idea, in spite of its impracticality. Those who think there is an inventor who will break Newton's laws in his garage next year are ripe pickings for the Mollers and Tilt Rotor advocates.