The namespace name will be Archived (numerical id to be determined) and its purpose will be to hold pages like "Subversion" that have the template "historical" applied to it. These pages would move info that namespace and you would get Archived:Subversion, Archived:Manual:Small padlock icon, Archived:Help:Extension:WebFonts etc.
This will give us a place outside of the main content namespaces to keep information about configurations, manuals, extensions and skins that we want to keep, but where it will no longer pollute our set of currently relevant information. The namespace will not be part of $wgContentNamespaces and $wgNamespacesToBeSearchedDefault namespaces.
Hopefully this will allow for a more searchable and better functioning
mediawiki.org when it comes to documentation for new users, while preserving history in the spirit of wikis.
I've discussed this with various people at various points in time who all seemed to think this was a good idea, but we've never really had an open discussion about it that could result into action.