We’re already seeing more wrapped BTC on Ethereum, than there is BTC on Lightning, so that’s very telling.
That makes sense; people want to hodl or trade, not spend.
Bitcoin has undergone pretty massive updates in the last few years. Proof of stake doesn't seem that far fetched honestly.
AFAIK, none of the Bitcoin updates in the last few years is a "hard fork", that is, old nodes can still process valid blocks made by new nodes (though they might accept blocks which new nodes would reject). Changing from proof of work to proof of stake would require a hard fork.