As you will read they have something else planned but it doesn't seem to be in quite the same league as our present groups (from what others have said who have checked it out!) ... however there are other alternatives available away from MSN.
Here’s Microsoft’s explanation for the shutdown:
The natural question to ask in this situation is why we are closing MSN Groups. It is our goal to provide our customers with the most current and user friendly technology available today. We made the difficult decision to close the MSN Groups service as part of an overall investment in updating and re-aligning our online services with Windows Live. In the long term we believe that closing the service is the best way to continue to offer innovative, best of breed services that help you stay in touch with the people you care about. It’s very important to us that you keep the data you created using MSN Groups and that is why we have partnered with Multiply, so you can keep your group going into the future despite the closure of MSN Groups.
The Microsoft post also states that users will have until February 21, 2009 to migrate their groups over to Multiply, after which point the site will cease to exist.