I think the most likely bands playing the festival will be ones with new albums out, giving them something to promote, along with not coming to DC in the months leading up to the show. Velvet Revolver breaks this, as they're playing 930 soon, but all the other announced acts fit into this category. That being said, likely acts:
White Stripes (maybe too big)
Bjork (maybe too big)
Amy Winehouse
Neko Case
Underworld
Chemical Brothers