Interesting point. The cryptocurrency energy consumption problem will never be solved, since if it is, it will be economically feasible to attack. So cryptocurrency adoption in the mainstream will require massive electricity consumption.
And then if that's true, one might dream of a power plant arms race, where two competing nations build additional power plants as fast as possible to prevent the other from gaining enough electrical capacity to attack the network...
Oh...
I'm not saying it's perfect -- there are some downsides like needing a cap on fork distance in order to prevent stake bleeding attacks [1] -- but it's certainly viable.