My quick thoughts on the quantum threat to Bitcoin: It is likely that we will settle on a hard fork because post-quantum signatures are significantly larger than current Bitcoin signatures, which would break backward compatibility. Following that, all Bitcoin would be migrated to post-quantum wallets. Questions remain, such as what to do with dust or large lost wallets, like Satoshis. I believe we should standardize a migration date far in advance, allowing plenty of time for the news to spread naturally. After the migration date, the new consensus rules could invalidate transactions from old ECDSA addresses by rejecting them outright. Don't be fooled, we have plenty of time to reach a majority consensus on a smooth migration process.