> The Bitcoin core devs can issue a word-of-god statement stating that they'll roll back the chain to before the attack, and all is well. Then they'll change the cryptography.

That doesn't work, because once the signature scheme has been broken, nobody can prove that their coins are theirs. No roll back or word-of-god would help.

The only way to make bitcoin quantum-safe, is to introduce a quantum safe signature scheme, to encourage everyone to move their coins and to somehow accept that those who don't are not longer in control of their coins.