Facebook chat also uses XMPP.
So in answer to your question: yes, there are people still building new stuff on top of XMPP.
However I will concede that I'm also a bit IRC advocate - so I'm probably the wrong person to comment on the best newest social protocols.
Better known as "reinvention of shit that already worked because we want to lock you into our platform and monetize your eyeballs."
I'm not worried that Google might someone how hack into my server and kill XMPP on that, nor am I commenting on the level of the Facebook Chat integration with the wider XMPP community (in fact the reason I run my own XMPP server was to have a private channel, so I can completely understand why Facebook have chosen to do so as well).
My comment was just stating that XMPP is still widely used - despite other peoples claims that Google were it's only supporters.
...
PLEASE!
:-D
(with apologies to Henny Youngman -- http://en.wikipedia.org/wiki/Henny_Youngman)