If Proof of Stake of Ethereum eventually becomes unfit, stakeholders would watch value worth of Ethereum token gone down the drain! The networks that make use of EVM of Ethereum will pull out to join other better networks. And drastically, Ether will witness decreasing use cases and low trading volume that will gradually shut down on its prices to the lowest ebb of market pricing which is a great seal of demotion and probably the demise of operations.