Bitcoin and POW sustainable does a POS is an option at all?
Proof of Work is how Bitcoin operates from the beginning.
The hashrate is so important for the safety and stability of the system together.
But it is known to be not so good for the environment because the need of lots of electricity.
Because of that and the need of electricity in our changing electrified life governments will be targetting Bitcoin and their miners as the countries need the energy. If it is excess energy then there is no issue but it is not always like this.
In theory it is possible that Bitcoin goes Proof of Stake but then the rich get richer. And for me personal this is a no go. As bitcoin is decentralised all devs and miners will have to work together for it to happen and as it is not an organisation this will be very hard to accomplish.