There was some discussion in IRC about dropping the ability for external clients to use the XMPP server: http://chatlogs.metabrainz.org/brainzbot/metabrainz/2016-01-06/?msg=3464354&page=2
Personally, this is fine to me, since I don't think it's an essential feature that many (any?) people have asked for, and we still have emails.
But if we're only going to use XMPP to pass messages around within our private LAN, I have to wonder what the point was. The main benefit of XMPP, to me, was that it was interoperable with different client apps. (Are there other important benefits?)
That seems like an important question to me, because as Gentlecat pointed out, there are a lot of things we need (authentication, storage) that we'd have to implement ourselves on top the of XMPP server anyway.
We're asking for public feedback on this bug report:
http://blog.musicbrainz.org/2016/01/29/notifications-and-messaging-in-metabrainz-projects/
If you care about this ticket, please comment on the blog!