Are you sure? From my reading, it's saying the exact opposite - XMPP clients still connect to a seperate XMPP chat service that's compatible with the App Engine XMPP support and completely seperate from Hangouts. The Verge also had a chat with the head of that department and he said that Hangouts drops XMPP support, apparently with no caveats about it still partially supporting XMPP: http://www.theverge.com/2013/5/15/4318830/inside-hangouts-go...