They’ve been betting it’s not for about ten years.

With these changes, I can imagine “intro to docker” tutorials breaking.

I suspect that’ll be enough to let a fork/competitor gain significant market share.

hm.. switch to fork just to avoid trivial, mechanical, 10-character change in docs and scripts? (image/name -> my-repo.com/image/name)

I doubt it.

The web is absolutely littered with docker tutorials and a huge proportion of them (not operated or maintained by docker themselves) would no longer be valid, I'm sure.

Oh great, so now it's a hidden default that might be different system-to-system. Disjoint from the actual deployment config. Please, dear god, no. I'm sorry, this is a bad idea.

It's just not that hard to go fully qualified.

If you specify the fully qualified image location then it's irrelevant. It's only when you decide to use short hand that it comes into concern