Apparently the power contained in aircraft fuel amounts to the equivalent of 12000Wh/kg, so even with the new batteries fuel has more energy. However, a combustion engine only turns 20-30% of that into power, whereas an electric motor will turn 85-90% of into power, so you'll never need to reach those power storage levels.
If the car industry is anything to go by, then the shift will happen pretty quick once things start getting in place. Just remember how quick the hybrids went from the car nobody wanted to the car everybody wanted. The Prius is a massive seller for Toyota and every manufacturer has some type of hybrid on the go.
Fast forward 30 years. A board is going to have to be pretty convincing and persuasive if they want the shareholders to approve the costs of a gas guzzling Gulfstream G650 when they could be riding in an electric or hybrid bizjet that might not be exactly as fast or have exactly the same range, but get you there for a fraction of the cost. Imagine the badwill. Not to mention that the carbon excesses imposed by government on fossil fuels by then. They're never gonna get cheaper, that's for sure.
Backwards and slow...? Slow, yes. Backwards, really?
No, on avionics I agree - there it's been pretty fast lately. Construction? Not so much. Remember, the first composite aircraft was way back in the 70's and it was an experimental. You'd think the military and the big corps would lead this, but in fact without EAA and enthusiast tinkering in garages worldwide, there would be no 787.