I'm guessing it's more that they're trying to push sales rather than money constraints. Because if it were that, they would be better off just simply leaving things off as they are - producing whatever needs to be for Gamecube functionality has probably become cheap and easy to cope with by this stage of console's lifetime.I'm guessing Nintendo is finally ditching GNC due to money contraints, much like Sony did with it's 20GB & 60GB launch models, well I can't blame them since there main focus will be on the upcoming Wii-U.
This step requires payment for a redesign and practically a new method of production down the factory line. All of which takes preparation. Plus unique packaging for the console.
Sales for the wii have been abysmal the last eight months. But with the coming holiday and the release of Zelda - what better compliment can there be than the cheapest console available, with a wise library already on the shelf? I think Nintendo can push Wii sales very far with the remodel.