I am confused by this as well I got the message on my phone through email and thought it was just syncing old stuff, but they even have a blog post for Sept 2014 about it. IDK if this means they are supporting the hangouts version of what gvoice will port to, but i just signed up for my first ever gvoice account and set it up on my obi and it works fine. I just called an chatted with a friend, and called my other phone, etc,. It seems fine here? I used the ObiTalk configuration tool it popped up the google login and i logged in and it all synced up.
I would love to know if this is means that google has kindly given Obi some help in maintaining a way for existing users. I read "Google Voice Now Supported" and thought welcome to approx. 2010/2011 when Obi shipped mainly for the gvoice users demographic, Also It forced me to firmware update before I could add google to it, that might be important I know.