lucianpilot,
I don't think jet fuel will be replaced anytime soon. But that's not to say we won't see practical electric drivetrains in rotorcraft in the near future. I've seen some developments in turbine electric drivetrains that were very impressive. The technology appeared to be competitive in terms of both cost and weight with conventional drivetrains, and possibly having better efficiency and reliability. It also appeared that it would scale up quite well to any current rotorcraft power requirement. I can't really tell you anything more specific about it, but I'm sure you'll see it flying somewhere in the next 2 or 3 years.
riff_raff