We announced a new communications product, Hangouts, in May 2013. Hangouts will replace Google Talk and does not support XMPP.
In addition to the Google Talk client, there are many other clients out there that provide a great communications experience. We believe users should have choice in which clients they use to connect to the Google Talk service and we want to encourage the developer community to create new and innovative applications that leverage our service. To enable this, Google Talk uses the standard XMPP protocol for authentication, presence, and messaging.