I don't know about federation, but to me matrix hits the right spot for people that want modern chat (irc with full history & e2e encryption) in-house. I know my org is using it heavily on a custom install. I think the French government also announced some time ago some kind of adoption. I hope we can get away from whatsapp, telegram, slack and anything Google when we want.

Only things missing (to me) is a full Java API. I built one for bots and quick fleet-history-monitoring, but it's clunky...