I agree, smash would show that there is a market for metal gear on nintendo. Considering all the votes snake is getting, Nintendo should show that to konami and that would be some good proof that there is a demand. I'd like to see them try again on 3ds (it'll probably sell better there.) I'd love to see a metal gear on wii u, but I don't think it'll happen unless Nintendo approaches Konami.
3rd Party support for wii u is a lost cause, exclusives are much better. I remember Kojima said that he'd rather make an exclusive for wii u than port the existing game. I'd like that, they could tailor it for the wii u. If we just got an mgs5 port, it'd be inferior to x86 platforms.
Majority of wii u owners own another platform. In an interview, Iwata now thinks of the wii u as good secondary console. Releasing a multiplat for the wii u is pretty much selling to the same people again. The only reason they would is if the wii u version was tailored for the gamepad, and majority of time when it is it's always delayed. But my point is, I'd rather we get an exclusive than MGS5.
Who knows, they might have game up their sleeves and plan on doing promotion with snake dlc or something, we still have that miiverse debug menu leak to fall back on.