isn't the kind of act viewers want to see at a Super Bowl. May as well just have a mime troupe play at the event, if that were the case. And she's far from being a revered musical performer, so I'd think they'd steer away from that- she made her guest appearance during Aerosmith's set years ago, anyways.
Madonna may be a bit too edgy for the NFL (and you know she wouldn't have apologized if her breast popped out during a performance). However, she's demonstrated that she can put on terrific shows, even without boundary-pushing, so, perhaps a consideration.