Sure there are.Are there any gas powered drones out there? That would be a way to extend flight. Bus as a old RC flyer I can tell you it is messy and hard to get all for motors coordinated with each other. As for more batters and wind generator that is a pipe dream as someone else has already stated. I am sure that if we live long enough there will be advances in technology that one day we might be there. For now be happy with the 20+ mins and buy extra batteries.
Reference Technologies
But not (yet?) in the consumer space. These things are REALLY expensive.