This is a press release with no evidence cited about XMPP's takeover. They do say there is some evidence in two linked documents, but both are behind pay walls. Where's the meat?
Gartner's business model: sell enterprise-friendly papers on the latest industry buzzwords; drive sales by sending hollow press releases to clueless business/IT journalists.
Gartner's business model is something along the lines of "make a prediction about tech $flavour-of-the-month to insecure CTOs with a timespan of about three years. Three years later, things have moved on and everyone has forgotten their prediction." Whether right or wrong.
Apparently you pay good money for these predictions.
If XMPP doesn't take over, then something embodying its good ideas will. That seems obvious to me. What form the eventuality will take seems up for grabs, though. Why Gartner would proclaim anyone the winner so soon is anyone's guess.
Yea sorry, but word on the street is that Twitter replaced XMPP with streaming HTTP connections because they found that XMPP doesn't scale. Something about the fact that a slow XMPP client can bring down the whole server because of messages backing up.
Allegedly Google Chat ditched XMPP too. Behind the scenes it's some proprietary system that is somehow compatible with XMPP for 3rd party clients.
Also, not to be a dick, but I don't think the founders of Diaspora are an authority on scalable realtime data.
Twitter had an XMPP gateway to send tweets. They were never built on XMPP.
Google still uses XMPP. On Android phones this isn't exposed as a service to other apps (if you want that, use Rene Treffer's excellent https://github.com/rtreffer/AsmackService).
Android's XMPP bits use a proprietary binary protocol to communicate with their XMPP server farm. Probably to reduce power consumption. You can still use any 3rd party XMPP client to connect into google's XMPP cloud.
