As far as I know, the DC coupon for National has not yet been extended to include any dates in 2003. (Just checked the DC website and that coupon still expires on 12/31/2002).
I'm just guessing, but I think any special DC discounts for 2003 will involve Alamo rather than National. Although both National and Alamo have the same "parent", Alamo is/will be targeted more to leisure travelers and National to business travelers.
Alamo was recently announced as the "Official Car Agency of WDW and Disneyland".