Well I think the vita can also achieve a stable user base even if it is low, that is like the lowest bar you could have set for the wiiu.
They can't get the price down to gamecube levels though, probably not ever unless they dump the controller screen completely. I guess removing your attempted usp is an extra option over the gamecube but I don't see them making that move and if they do it will be a long time from now.
what we've seen with the 2ds, worldwide release of pokemon, insane price cut of the 3ds, dropping the price of the wii u and bundling it with an unreleased remake, shoving 3d land and mario kart 7 out the door, and greenlighting nsmb2, is that nintendo is very in tune with options to make their hardware sell.
i feel that the ten months from launch to pikmin were an acknowledgment that there wasn't going to be an upside, maybe for a long time. iwata admitted as much in the end of his fiscal year investors meeting. knowing that, i think they have to be considering the idea of dropping the gamepad in a way. just enough that they can get the wii u to a much more affordable price, and make the gamepad the wii fit board of the wii u. this is very likely a last resort, but i can't help but think it's been something on the table.
Xbox 360 became a kids console just fine at the end half of its life, i don't see anything stopping ps4/xb1making that transition
i don't see anything helping them making that transition either. maybe skylanders a bit. not knack. never knack. but seriously, the biggest obstacle is the price. a $170 handheld wasn't doing it. i don't think a $500 or even $400 console will do it.