Out of curiosity, I checked the certificate expirations of the only two GfW games that I have installed:
Bioshock 1.1: 5/10/2007 to 5/10/2008
Fallout 3 (RTM): 9/16/2008 to 9/17/2010 (launcher and game executable)
Bioshock probably isn't a problem since it doesn't connect to GfWL. However, Fallout 3 does. I'm guessing that they'll update the executable with a renewed cert in a future patch, lest they follow the same fate as Epic.