It's way to early to say whether or not a game will support Windows7. A lot of companies got burned hard with Vista when they said they'd support it and had been working on supporting it for months before the launch of Vista only to have Microsoft make major changes to the launch version that made 90% of the programs that had been using the dev kit completely incompatible.

I think this time around you'll see companies wait until AFTER 7 has launch to claim whether or not they'll be supporting Windows 7. I know my company is.