Its early days but this is sure to be the future for R/C Electric & Multirotors...recharge in seconds.
http://www.wimp.com/supersupercapacitor/

It really all comes down to capacity per weight unit.
Good LIPO's are just above 150 Wh/kg, and I think the super/ultra capacitors currently on the market are around 5.5 Wh/kg.

The coming Lithium Sulfide rechargeable batteries will hold around 450 Wh/kg - Yes, that's tripling modern battery packs' capacity
My guess is, these kind of cells will hit the market in a year or two..

But compare it to gasoline, which holds around 12200 Wh/kg, or Liquid Hydrogen: 39000 Wh/kg (without container, valves and engine/fuel cell).

I still like the idea of burning some kind of fuel, as it decreases the flight weight while used. Preferably in a fuel cell, since they have the greatest efficiency. But the technology just isn't there yet, the numbers still don't add up right...

http://news.rice.edu/2012/11/01/rice...d-batteries-2/

this is very promising also.

Good data Mr Dane...

History has taught me, that is there is a demand for something, someone will figure out how to make it work… There is a huge demand for better batteries, no question… for full size cars, cell phones, laptops…. Ect… Its only a matter of time before 45-60 min flights are common. I would rather HD video to fly FPV… because 17 min is long enough for my flights…

Eddie

From what I've read, I assumed the next big jump in Lithium energy density would be Li-air or Li-O2 technology. Even the suggestion Wh/kg would compare to liquid fuels. Add to this the possibility of carrying capsules of 100% O2 to be analogous to nitrous used in top fuel racing systems.

I understand a real-world application of the tech is formidable, but it sounds as if it would be a grand game changer if it could be made practical.

@Mr Weeks:
It's not my data, but maybe some documentation for my numbers is in order.

Cyberdactyl is right, the theoretic maximum for Lithium batteries is in the magnitude of 10000 Wh/kg (source)