Every major breakthrough in quantum computing gets hailed as “the end of Bitcoin” except for the part where people conveniently forget that if some computer can break the math that secures Bitcoin, we’re all in big trouble anyway. That same math secures the entire traditional banking system, all the encrypted websites people rely on, all the military communications, and all the passwords people store online.
I get this, but there is a little difference: the convenience and speed of an upgrade to QC-resistant cryptography.
Banks often use SaaS cloud software platforms, or at least quite standardized software. The software vendors can simply upgrade the cryptography and then the platforms would be secure again. And the signature size isn't so much a problem too.
On Bitcoin instead, an upgrade potentially can take a lot of time. Not because simply integrating FALCON or some other cryptosystem would be a really big deal, but because all "quantum resistant" protocols have big signature sizes, and thus you will have to try to integrate this in the plan, because if everybody rushes to upgrade from ECDSA to FALCON we would run into a huge block space bottleneck. We would probably need a new Segwit witness discount for these signatures. And have to estimate how high will be the additional blockspace needed for the "transition rush" as a lot of people would like to secure their funds ASAP.
Then there has to be decided if there's done something with P2PK and other vulnerable outputs, or not, which can lead to heated discussions and even to a hard fork.
So the planning for the post-quantum world is a little bit more complex in Bitcoin. But I agree that it's overdramatized. From today's point of view addresses which were not re-used are safe and there are
ways to protect and move them even if a QC exists which can hack a key in 10 minutes. All solutions are on the table, with the exception of P2PK and friends where probably no ideal solution exists, but a redistribution of old "lost" funds would also not kill Bitcoin.
