The reason ETH hasn't yet switched to Proof of Stake despite having planned to do so for several years is because it doesn't work.
This is where Hybrid PoW+PoS comes in, and might just be the most likely answer. They have been thinking about the switch to ProgPow. Let's see how that goes.
Do you think that ETH will change the algorithm for progow? And maybe before he goes to the pos?