Let's face it, Mario 3D world look totally subpar compared to the previous Galaxies. The Wii U is selling quite badly and this subpar game won't be a true system seller.
I predict the game to be the worst selling game of the serie. It will sold less than Sunshine and NSMBU. I think that it will sell 2.5-3 millions LT, which would be a big failure for platform Mario.