This is the big question. Miners are replaceable. Replacing Core would be nearly impossible. I think more people who signed it will flake out as the time comes until it's clear that the creation of yet another Bitcoin will be inevitable. That definitely wasn't their plan so it's likely the idea will die off.
Is your thinking that the miners will change their position based on their concern about losing the core developers? The miners seem like pretty independent and strong business personalities to me but maybe they have a more long term affinity for well laid crypto theory than I thought.
And suggesting POW change to them reminds me of how well our negotiations with N Korea are currently going.
If the miners stay together the exchanges are probably likely to stay because they need volume stability for their trades. (I would imagine).