Sorry for my misunderstanding. Then we agree.
Right now the proposal is to improve the API: namespace in
mediawiki.org,
instead of creating a new Dev: namespace in
mediawiki.org. See and join
https://www.mediawiki.org/wiki/Project:Current_issues#Adding_a_dev_namespac…
The very initial plan was to have a new site indeed, but that was a long
ago, and I pushed (hard) to go for a solution integrated with
mediawiki.org.
Ah, cool. I missed that.