Not Beta
It's not really fair calling EVs "Betamax". Betamax was a specific format that couldn't be changed, no ability to improve and evolve. With EV's, the critical part is the battery pack, and that is entirely open ended. As new and improved battery formulations come along, there is nothing preventing EVs from using them, so that is a completely different situation than what was Betamax. The limits of battery capacity set by physics and chemistry are something like 100 times where we are now, so a 2x, 4x, or more increase is not at all unreasonable to expect in the future. How long that will take depends mostly on how much R&D effort we decide to put into it.
And to me, hydrogen is not like HD DVD, it's more like when I was a kid and we all assumed that the future would be full of flying cars or nuclear powered cars. Sure, it is actually possible to make a nuclear powered car, but would it ever be practical?