For the past 15 or 20 years, every couple of years some astonishing new breakthrough in electrical power storage -- often some variety of supercap, but just as often a new battery technology -- gets announced with much fanfare and hoopla.  Then reality sets in, and it turns out that the technology is a lab queen that can't survive the rigors of the everyday world, or has to be hand-assembled by gnomes, or something.

So I'm skeptical.  Not disbelieving -- LiPo batteries were part of that crowd until they distinguished themselves by actually working as promised -- but I'm not going to put off buying my next set of batteries, either.

Capacitive energy storage would put interesting constraints on the electronics, because while battery voltage does drop a bit as the energy is depleted, capacitors drop voltage a lot: at 50% depletion the voltage is about 70% of the starting value, at 75% depletion the voltage is at 50%, at 90% depletion the voltage is down to 30% of the starting value.

So it's good to keep your eye on it, but don't get too excited yet.