[qes]

I think 2017 showed that it will be damned difficult politically to make any change that requires a hard fork to Bitcoin anymore.

Pure proof of stake is fantasy. That's not "Bitcoin" and it never will be.

My personal hope would be that mixed proof of work and stake with on-chain governance, like Decred (their devs have built much of the Lightning Network tooling, performed the first cross-chain atomic swap, etc.) - could be adopted; but, realistically, I think that's also a fantasy.