Really looking at that trend... without some crazy change in marketing, content, price, etc... WiiU should has a hard time even reaching 3m sold and with that I doubt there will be 1m on shelves. More likely only ~500k. Meaning shipped is going to have a hard time reaching 4m. For them to make this estimation, they have to have something else in the plans.
Based on Iwata's most recent statements, there is no price cut coming as its already losing money per unit.
We also know that no big games are launching before March and only one month of a couple new games can't be their plan to surge sales.
There has to be something planned for February if they expect to increase sales to a level where 4m is plausible.