A theoretical change to the Bitcoin consensus mechanism from proof-of-work (PoW) to proof-of-stake (PoS). Bitcoin proof-of-stake would be like the change Ethereum made in 2022 (see
Ethereum 2.0). However, changing from PoW to PoS would be a more massive undertaking than Ethereum's change because Ethereum did not require specialized hardware for its PoW mining.
The hundreds of thousands of Bitcoin mining rigs operating throughout the world would theoretically become useless unless they could be retrofitted for other PoW blockchains, none of which are close in market cap to Bitcoin. See
consensus mechanism,
Bitcoin and
Ethereum.