I hate Scott Moffitt, but I think he is partially correct. With the right support I don't see why the Wii U couldn't garner at least GC level sales.
Because of sales trajectory.
GameCube, Worldwide Shipments as of September 30th, 2001 (Japan only):
.51 million hardware, .71 million software
GameCube, Worldwide Shipments as of March 31st, 2002 (end of 1st fiscal year):
3.80 million hardware, 14.37 million software
GameCube, Worldwide Shipments as of September 30th, 2002:
6.68 million hardware, 34.58 million software
GameCube, Worldwide Shipments as of March 31st, 2003 (end of 2nd fiscal year):
9.55 million hardware, 60.51 million software
Wii U, Worldwide Shipments as of December 31st, 2012:
3.06 million hardware, 11.69 million software
Wii U, Worldwide Shipments as of March 31st, 2013 (end of 1st fiscal year):
3.45 million hardware, 13.42 million software
Wii U, Worldwide Shipments as of June 30th, 2013:
3.61 million hardware, 14.44 million software
Wii U, Worldwide Shipments as of September 30th, 2013:
3.91 million hardware, 19.71 million software
Wii U, Worldwide Shipments as of December 31st, 2013:
5.86 million hardware, 29.37 million software
Wii U, Worldwide Shipments as of March 31st, 2014 (end of 2nd fiscal year):
6.17 million hardware, 32.28 million software
The Wii U is significantly lagging behind GameCube in terms of both hardware and full-priced software adoption.
It's trending to underperform relative to the GameCube...these trends don't just magically reverse themselves with Nintendo staying the status quo.
We have already seen releases of major IPs from last gen including Wii Party U, Wii Fit U, Wii Sports Club, Super Mario 3D World, Super Mario Bros. U., etc., and none of those had a real effect on reversing this trend.
So why should MK8 / Smash Bros. be any different?