Clients need to be updated, too, since what's happening is that the server and client need to agree on a common algorithm they both support, but that's been in progress for years and support is now pretty widespread in the current versions of most clients.

Stragglers are a problem, of course, but that's why I thought this would be a harder problem for Bitcoin: for me to use PQC for HTTPS, only my browser and the server need to support it and past connections don't matter, whereas for a blockchain you need to upgrade the entire network to support it for new transactions _and_ have some kind of data migration for all of the existing data. I don't think that's insurmountable – Bitcoin is rather famously not as decentralized as the marketing would have you believe — but it seems like a harder level of coordination.