After Google Wave, the company will again use XMPP, now for their Chrome browser's sync feature. Together with GTalk, this is the third high-level technology from Google featuring XMPP.

My guess is, it will only be a question of time until browsers will offer built-in XMPP protocol support, making HTTP and AJAX more or less void (I'm not kidding).

Greg Wilkin appears to be right when he notes that Wave will only use XMPP for server-to-server communications. Sync is planned to exploit Google Talk. And Google Talk does support client-bound XMPP connections. Of course, in the browser, the transport for XMPP is still HTTP.

At Apache, we've already started building an open source XMPP server, with my two heros Michael working on PubSub and Niklas starting implementing MUC - Multi User Chat (IRC done right). It's hosted at Apache MINA.