The existence of feedback loops very much doesn't imply a stable equilibrium. Actually, any system that is not overdamped will necessarily not reach an equilibrium.
Or maybe the equilibrium is that no country bans it, and PoW currencies don't die on their own due to lack of financial rewards, and PoW artificially inflates the demand and therefore price of energy, leading first to widespread economic issues, then widespread ecological issues, until there is no one left buy pizza from with your BTC. Very compelling equilibrium.
point is that it's not a closed system that just blows up at some point. as long as there are people interested in keeping bitcoin running - it will keep running. for now economic incentives are enough, and it'll probably be enough forever, worst case - ideological incentives will do it.
Or maybe the equilibrium is that no country bans it, and PoW currencies don't die on their own due to lack of financial rewards, and PoW artificially inflates the demand and therefore price of energy, leading first to widespread economic issues, then widespread ecological issues, until there is no one left buy pizza from with your BTC. Very compelling equilibrium.