It's actually available now (the free content) and some people, like myself, found their USB stick woroked anyways! Pretty sweet deal to get $10 free.
Just prior to the launch of the limited edition of Splinter Cell, developers UbiSoft announced a $10 price cut. This is mainly due to a malfunctioning of a USB drive within the package. But the content of the USB drive, they say would be available for download to those who lay their hands on the faulty drive.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic