I already suspected the problem when I first had the misfortune to run into Hangouts a couple of days ago. That suspicion is official now. Talks federation with other servers is a matter of the past. Hangouts will not support it and thus all your non talk contacts will no longer be able to contact you. Or you them for that matter. Hangouts for now supports XMPP with Google only. So at least you can use another client for text only.