I dont see how Wii U can outsell anything, Sega Master System (13–14.8m) is last console that Wii U will outsell.
Nintendo made so many mistakes around Wii U and we already know they will correct majority of those mistakes with NX.
We don't know enough about NX to predict sales numbers, but I am sure it will sell much better than Wii U. I finding its nearly impossible to sell worst or same like Wii U.







