TexasYankee

Here is the wording at the top of the sign up form (I get 2000 miles as I have a NWA signature visa)

For $20 you can SuperSize your next paid roundtrip on Northwest Airlines®, Delta Air Lines, Northwest Airlink or KLM Royal Dutch Airlines and earn 1,000 Bonus Miles. And, because you are a WorldPerks® Visa® Cardholder, you will earn an additional 1,000 Bonus Miles for a total of 2,000 Bonus Miles*. These Bonus Miles are in addition to the regular credited flight miles you will earn for your paid travel.

With the help of Northwest Airlines, WorldPerks Visa and the WorldPerks SuperSize promotion, you'll get connected to award travel even faster!

* All flight segments within the paid roundtrip must be operated by Northwest, Northwest Airlink or KLM Royal Dutch Airlines to earn the SuperSize mileage credit. Bonus Miles are banked miles and do not count as credited flight miles toward Elite Status.

and the rules at the end of the form:

SuperSize Offer - Terms and Conditions:

Prices are quoted in USD.
You must be a resident of the US50 or Canada to participate in this offer.
SuperSize purchase must be made prior to the roundtrip flight.
Only one (1) SuperSize purchase can be made per roundtrip flight reservation.
Multiple purchases of this SuperSize offer cannot be applied to the same roundtrip flight. Instead multiple purchases will apply to subsequent roundtrip reservations.
Only paid tickets where member claims and earns WorldPerks miles may qualify for this offer.
SuperSize purchase is not applied to a specific reservation; SuperSize is tied to the first roundtrip flight after making the purchase. 2,000 SuperSize Bonus Miles will be awarded after the completion of the roundtrip flight.
You received this special Bonus Mile offer (additional 1,000 Bonus Miles) because you are currently a WorldPerks Visa Signature, Platinum, or Business Cardholder.
Qualifying travel must take place between purchase of offer and December 31, 2009.
All flight segments within the paid roundtrip must be operated by Northwest Airlines, Northwest Airlink or KLM Royal Dutch Airlines to earn the SuperSize mileage credit.
This is a special nwa.com-only offer. This promotion is not offered through Northwest Airlines Reservations.
This offer is not retroactive and is non-refundable.
Once purchase has been made, no refunds are allowed for the SuperSize mileage purchase regardless of flight activity.
Bonus Miles do not qualify for Elite status.
Reference code: GNWP SUPERSIZE
Northwest is the final authority on the interpretation of these rules.

so it seems that the program is on through 2009 if you at least fly NWA. I will know about Delta in 3 weeks. More then.