I really have to question how NPD is planning on accounting for this. A huge promotion during one of the busiest shopping times of the year is not something you can exactly predict easily.
With a thorough history of data it can be done and done accurately, but the scenario we have here is a console selling at an unprecedented rate, with an unprecedented promotion during a normally unpredictable time of year.
I think they stand a very good chance of undertracking the Wii this week, particularly Wii software.