The specter of quantum computer systems is especially that they’d break Bitcoin’s elliptic curve cryptography, which means they might derive a non-public key from a public key. There’s additionally the potential risk to mining, however I consider that is far much less understood (it definitely is by me), so the next applies mainly to the elliptic curve cryptography.
The final answer to the quantum risk is to introduce a post-quantum (PQC) signature scheme, which may very well be completed with a comfortable fork. Then, everybody must migrate their funds to the PQC scheme in time earlier than the quantum risk materialized.
The query then turns into what to do about cash (UTXOs) locked with weak public keys. One choice is to do nothing and let the cash finally be stolen by quantum attackers. Another choice is to make these cash unspendable with a comfortable fork after a set deadline. But an alternative choice is to make these cash unspendable utilizing the weak signature scheme alone, and there are a lot of solution to go about that, however all of them may very well be completed with a comfortable fork.
The one time we would wish a tough fork is that if we might first need to make the weak cash utterly unspendable with a comfortable fork, after which later wished to re-enable spending with a safe signature scheme. Until the specter of quantum computing materialized immediately and unexpectedly I do not suppose we might try this (and we would have greater issues anyway).
