Gotta love store errors.
http://www.wiiloaded.com/MGS4-listin...MV-t-10882-wii
Look at this tidbit from the MGS4 for 360 page.
Number of Discs: 1
From the way that Kojima has talked and how he had to cut content from MGS3 to get it to fit on a DVD, I highly doubt that it would fit on a DVD9.