What do we do when Google shuts down Google Groups? I have no particular information that Groups is about to get the axe but I sure wouldn’t bet on it sticking around. Google is shutting down social products that don’t fit their Google+ strategy. And Groups has never gotten much love; it's poorly staffed and the product keeps getting worse. (The site is still touting “the new Google Groups” that’s over two years old; some of the links documenting the “new” features don’t even work!)
The obvious casualty of a Groups shutdown are the communities that use Groups to communicate. But there’s plenty of alternatives: Yahoo Groups, Facebook, maybe even Google+. These products aren’t great; despite how lousy Google Groups is a lot of people still choose it. But I think the market will provide. Migration would be easier if Google offered data export: I think you can get list members but not messages.
But the unique thing Groups has, the thing that’s really important, is the historical Usenet archive that grew out of the Deja News purchase and later supplemented with other donated archives going back to 1981. Usenet is a pale shadow of its former self, but in the pre-Web days Usenet was the place on the Internet for people to communicate. A lot of science, culture, and community happened there and Google has the only easily accessible copy.
Google’s Usenet archive is important, but it’s not commercially valuable. And Google hasn’t been very trustworthy in keeping products like that around. I’d love to see a plan announced now, before there’s a fire drill, to gift a copy of the Google Usenet archive for preservation. The Internet Archive would be a good steward, or maybe the Library of Congress. Someone whose mission is to safeguard the world’s information, not just sell targeted advertisements on it.
Update: Jason Scott pointed me to archive.org's version of the University of Toronto Usenet archive for 1981—1991. It's not complete and Google did a lot of improvement, but it's one of the most important sources for early Usenet. It's great it lives outside of Google Groups.