The move was inevitable especially since the team was no longer working on Beluga and the service was just going forward based on inertia.
The announcement started off "We're excited to announce that we just launched the Facebook Messenger app worldwide in 22 languages! If you haven't used it yet we hope you'll give Messenger a try it has all the great features of Beluga and it's available on iOS, Android and BlackBerry ." .
It said "Now that Facebook Messenger is available everywhere we've decided to stop offering Beluga as a separate service. You can keep using Beluga for now but we'll be phasing it out over the next few weeks ." .
The first phase of the process will be on November 11, when Beluga will stop working i.e. you won't be able to send any more messages though the app and site will still be accessible.
That's a good time to start packing and get your stuff out of Beluga since it will be shut down completely on December 15, making all of the content unavailable.
You can grab an archive of your pods over at belugapods.com/getarchive if you need them. If you have something important in there you may want to hang on to it and grab it now since everything will be deleted in December.
Facebook Messenger replaces the need for Beluga and the Facebook integration helps so users will probably not be missing it too much. Of course there are plenty of alternatives to Beluga group messaging apps were quite the fad a few months back.