BTC hashing: I heard somewhere between 80-90 percent of all BTC hashing was in China, as of late Aug this year.
So if those miners are shut down (is ASIC mining really that hot of an electrical power issue?, big assumption in some ways) then BTC would be easier to corner all hash power and be able to control the network.
POS changeover is a huge hurdle for ETH, but they have almost unlimited resources to work with now, so I assume they will do so successfully.
And in fact, it's interesting (!) to read Dan's comments on the ETH spec for POS.
He is the only person I have seen actively criticize it; if you look through his posts you will see it.
I assume it is in his interest, to see ETH last at least until the middle of next year ;-)
Well some magic mining wizard can always turn up and save the day.