I think there's a conflict of interest issue here that would prevent such a move even if it would be worth it - the miners clearly have an incentive to keep the current PoW mechanism, as without it they're left holding a bunch of expensive useless tech. And without the miners willing to go along with a move from PoW to PoS, at best you're going to get a split between the PoW and PoS chains rather than a clean shift from one to the other and just create a mess, which isn't ideal for anyone.