Glad that it seems most people chiming in are aligned on the general outline I wrote up there 
Right, definitely it is a quite focused and quality>quantity group of projects. With the location of things though, it is not quite binary good or bad, since people are involved, and we're/they're fuzzy beings – so it is as much (if not more) about managing expectations and impressions.
I pointed out a few downsides of forcing the single location, and not even mentioning that it is not status quo anyway already – e.g. with NIO living under apple/... and perhaps other projects which may also live under such namespaces). One tends to put everything into the same bucket if one wants to claim that it is "my bucket" (e.g. if you're a software vendor, and want to show "buy my bucket of libs" etc), though we don't really want to play that game -- we want there to be many successful buckets, and some of the projects in them, we want to give special attention.
It's less of a problem than you might think; I've done that in practice with a few widely used projects, one example being (~17k downstream dependents on github, and many more in companies): GitHub - git-commit-id/git-commit-id-maven-plugin: Maven plugin which includes build-time git repository information into an POJO / *.properties). Make your apps tell you which version exactly they were built from! Priceless in large distributed deployments... :-) which used to be GitHub - git-commit-id/git-commit-id-maven-plugin: Maven plugin which includes build-time git repository information into an POJO / *.properties). Make your apps tell you which version exactly they were built from! Priceless in large distributed deployments... :-) Note that the "old URL" still works
Side note about "evil lib author," which could technically happen; In reality it does not change much where a lib lives, owners/admins can be added/removed anywhere etc.
The same just-works™ when depending on such repo via github url. I do not know if such renames work on GitLab, though another migration of major projects was between orgs without removing old one, just archiving old, and also worked out okey (esp. if tied timing wise with "next major version" etc).
Hope this helps,