Embedded in a flash site is apparently the Japanese release date for Final Fantasy XIII. That release date is December 17.
Thank URL twiddling. The flash site's URL had "_Before_" in it, and typing "_After" seems to bring up this image, which clearly states that the game goes on sale December 17, 2009. Previously, the title was announced for "this winter".
The rumored date is Japan only.
This release date is still unconfirmed. However, as local YouTube ads point out, Square Enix will be announcing the title's Japanese release date today.
Thanks everyone who sent this in!