Good first-principles argument, but in practice, this happens in ecosystems that do have namespaced packages. Off the top of my head:
- Until recently, kennethreitz was a GitHub organization so other people could manage kennethreitz/requests etc.
- Foursquare's Android app is still com.joelapenna.foursquared, which originally was a third-party app that got adopted by Foursquare and turned into their official app. Joe never worked for Foursquare.
- When Linus took a break from Linux development for 4.19, Greg K-H still released it from https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin... and https://github.com/torvalds/linux .
Probably more realistically, you'd put a note in your @delinka/ExcellentPackage repo readme saying that the package is deprecated and to use @fredralphbob/ExcellentPackage instead going forward, and simply not publish any more new versions. In fact I'm pretty sure npm has a built-in system to warn users of a package that its canonical name has changed.
Yep, we still have people who would eschew best practice and go against my method above, but that happens everywhere. Just because a solution isn't perfect doesn't mean it's not an improvement.