If bitcoin stays true to its ideal of being "trustless", it wouldn't move to PoS.
Because Proof of stake needs atleast some level of trust about who the validators are.  An entity can easily (relative to a 51% attack) fool others to believe in the malicious set of validators.

We are still far away from a full fleged implementation of PoS. Casper on Ethereum seems to be the best bet in the space. That too does budge from some ideals.
Given that, i think Bitcoin Maximalists won't make the move to PoS.

The energy consumption remains a valid concern. I don't think PoS is ready to be adopted to trade the security that comes with the energy burnt.