I disabled the Hangouts app on all my mobile devices and use Xabber (Android) instead which works fine talking to google. On the desktop I use pidgin. Both are using XMPP behind the scenes.
Google still didn't kill Talk which is XMPP conformant and even federated. But their Hangouts protocol is different and their Hangouts client doesn't use conformant XMPP. And since many users automatically got switched to it, they became cut off from their non Google XMPP contacts.
Nothing is over for XMPP until a better open alternative comes out. If Google see their Hangouts as a way forward, let them open the protocol and pull it through IETF to make it a standard. Oh, they are too selfish to do it? So they can get lost then, it's not an XMPP replacement.
No one else is eager to do anything like that as well, so XMPP remains the only candidate at present.