"All APIs can benefit from API management, realtime or not." Amen to that! :-) It's good to see this kind of thing coming to realtime, although it's kind of sad that some of the backend services mentioned don't have support for WebSocket yet...
Some Ns are larger than others. :-) At Talky, we can scale up to 15-25 participants using the excellent Jitsi Videobridge as a selective forwarding unit, and the results are similar at Jitsi Meet. Even at that relatively small scale, your browser might melt down depending on your hardware. Beyond ~25 we'll need to look at something more like a broadcast scenario a la Hangouts on Air (e.g., do you really need 25+ people actively participating and sending video at the same time?). As gz5 notes, that might imply a need for session control and moderation queues and such, or a larger group of passive audience members with the ability to temporarily grant send privileges to select users as needed. Those are all fun problems to solve. :-)
Most of the XMPP network switched last year to REQUIRING encryption for one server to talk to another server. Google doesn't support encryption at all for server-to-server links, and thus servers like jabber.org (of which I'm the admin) can't talk to Google anymore. See more at https://github.com/stpeter/manifesto/blob/master/manifesto.t...
Actually we (most of the XMPP network) switched over to mandatory encryption last May and IMHO it's been pretty successful so far. Google is welcome to join the party anytime! :-)