Thinking about this some more. Matt, let's assume your proposed solution gets implemented, and new quantum resistant addresses are created through a soft fork. It's tested in the wild over time and no coins are frozen. It's voluntary. Some people move, some don't, and some coins are dead and can't move. Then quantum hits. Someone with a quantum computer start grabbing all the remaining coins, including Satoshi's. They then move those coins over to the quantum resistant addresses. Is that the best option? Giving the quantum guys all that corn? Plus it could be a government. I don't have an answer to this question, but having some sort of cutoff date before quantum hits doesn't seem completely crazy given the alternative. I will admit however that coming to consensus on a cutoff date would seem nearly impossible.