What would happen to the X.pages.dev subdomains when they get auto-migrated? Do they get switched to X.workers.dev silently? My main concern with this sunset is about link rot for those who didn’t use their own domain.

Another concern is whether you’d still be able to get unique .pages.dev subdomains per project, it seems that workers force each account to one subdomain only across all projects. When pages get sunset dies it mean that you’ll no longer be able to make new unique pages.dev subdomains?

Also, the killer feature for many is the ability to just upload a zip hassle-free, both for production and for preview branches, the preview branches potentially serving as an extra subdomain level namespace. Would Workers still support that no-fuss workflow?

Sorry but I think there's still a basic misunderstanding here.

Pages is not going away. It is not "sunsetting".

What is happening is, the implementation is changing to be more closely integrated with Workers.

At present most Pages features are available directly on Workers, but not quite all, but we're working on it. Hence, we're suggesting people use Workers for new projects, but we're not auto-migrating people yet. Once we're feature-complete we'll auto-migrate people to the new implementation.

But the "Pages" brand will continue to exist, as a more-integrated part of the Workers platform. pages.dev will not go away. We will not break anyone's sites. Everything you can do with Pages today should be just as easy if not easier on the new implementation.