Well, this is what happens when a large corporation needs to put out an announcement: some technical product managers and/or engineers write something. It then needs to go through corporate legal and PR departments for approval before release to the public. By the time it has been repeatedly edited and "sanitized", it loses precise meaning.
Then, some tech blogs and forums (cough DSLReports cough) pick it up, and uninformed, opinionated users start flailing around with speculation.
The context of the announcement related to text messaging, and to users who were still using the very old Google Talk software. Google announced years ago that they were discontinuing the Talk and Chat client software. This is now the final step. The announcement wasn't focused on VoIP calling, and thus, it did not address that scenario.
There is nothing in the announcement about discontinuing third-party XMPP use for VoIP. The announcement is to let users of Google's own Chat clients know about the change.
Obihai's post above reinforces that. For those who wish for a definitive answer, you may not get anything more, but I have asked one of my contacts at Google if they can comment on this.
