It's going to top 10M in CY 2013. Wii U should have atleast one AAA title to boost the sales before the end of march; Wii Fit U.
Will that boost sales? I can't see people feeling the need to upgrade wii fit to wii u fit. It's not like you bought Wii Fit for the graphics, so why upgrade? This is the major downside nintendo never considered when they focused on the casual audience; getting them to upgrade when you are no longer the "in" gadget is incredibly difficult.
It's not the graphic increase but the little device it comes with that is going to be the sales driver. Go look up the game. It's kind of intriguing. Certainly not the level the first game was but it should sell well.