Actually not sure about that yet... I wonder if it means their internal server dropped XMPP.

I pushed Hangout to my toy Android phone, it replaced Talk. However My Pidgin and Pre 3 both still connect just fine, and messages sent from there gets updated on Hangout, just like on Talk.

If anything the article says that there is "some level of interoperability with Talk", so I think that means this new Hangout is just Talk integrated into bits and pieces of G+ (the picture sharing and 10-person conference) into a different app.

The other big hint is that Google+ is NOT mandatory to use the Hangout app.