It won't be Japan where the huge decline takes place. The Wii U is massively behind the Gamecube WW right now and once Nintendo's so called big hitters are out the system will collapse again with nothing else to prop it up. Unless Nintendo manages to find some support, we''ll be looking at a perpetual cycle of boosts with big games and then abysmal numbers the rest of the time and some bumps for holidays thrown in
So, since we're talking about stuff to prop up the Wii U in regions other than Japan, how much did the GameCube's third-party support contribute to its performance in the West then? Maybe I remember wrong, but I don't recall third-party games saving the day to maintain hardware sales in between first-party releases.
The Wii U won't be getting the Assassin's Creed's and Call of Duty's and Grand Theft Auto's etc. that are capital to PlayStation's and Xbox's successes. But those seriously don't mean much to a Nintendo console. I think the Wii U will keep getting stuff like Just Dance, Skylanders, Disney games, Sonic games, Rayman/Rabbids games, cartoon-based games, animated-films tie-in's, Angry Bird-type stuff and so on. I don't think it takes much more to carry a Nintendo system between first- and second-party releases past the 22-million-unit line.
Even when looking at the 3DS, how's its Western third-party support again? Is it that much better than the aforementioned franchises and genres? I wouldn't say so. Nintendo is stronger now than it was before the GameCube launched, and the few third-party games it gets are more important than those the GameCube got.
So I think the only way the Wii U doesn't outsell the GameCube is if Nintendo keeps screwing up their release timing like they did up 'til now. I think 2014 isn't looking too bad on that front. I'm not saying "not too bad" as in "yeah this will get them to another hit console," but good enough that I don't see the Wii U finishing its life below the GameCube and the Vita.