http://kotaku.com/5951552/the-xbox-360-gets-a-50-price-cut-at-gamestop-beginning-tomorrow
Kotaku has heard from a source that, beginning tomorrow, the Xbox 360's 250GB configuration, and the 4GB bundle that includes the Kinect sensor, will both get $50 price cuts at GameStop beginning tomorrow, lowering their price to $249.99.
Additionally, Cheap Ass Gamer has heard the same thing according to this forum post.
We've reached out with additional inquiries as to how long this price cut will last—it seems to be only for GameStop, though, not an overall product price drop.