most likely this just indicates ties towards the two companies working together for the NX. the reality is that Square Enix has gotten pretty good sales on Nintendo handhelds with a few franchises (Final Fantasy / Kingdom Hearts), and that they most likely are quite interesting in the possiblility of the NX and it being a crossover with potential for good sales
a mainstream Final Fantasy game (re-release or otherwise) on a system that is compatible for handheld version and home console could sell really well considering Nintendo has not really had many mainstream FF game releases in a while (besides a bunch of rereleases of the originals)
it's a pretty famous character though, I don't see what's wrong with him being in the game. bear in mind that almost all of Smash's character roster still remains Nintendo IP
