I do subscribe to, "We don't know what we don't know".
I agree with you that electric and/or hybrid aircraft will become widespread but I disagree that we don't know what we don't know, at least in broad terms.
Batteries of various types have been around for a long while; the main issues with them are longevity and energy density. There are physical limitations on the energy density of the Lithium Ion cells that are currently used to power aircraft and they'll never compete outside the training/microlight/powered glider markets. There are chemistries such as Lithium-Air that could be practical in terms of energy density for longer range aircraft but thus far they've been hard to develop. Ditto for fuel cells. Will they become practical? Maybe. But the basics of electrochemistry are well understood and there are hard limits on what the technologies will be able to achieve.