Ze Diglett
: ... but Nintendo doesn't own Geno. Square does, and they have every right to say "lol no" if Nintendo asks for him. They hold the power and they have every right to use it if they don't see his inclusion benefiting them enough. (And, let's face it, Nintendo would probably get most of the credit from the fanbase for managing to get him, and he might be classified as a
Mario series character in-game, which knocks out most non-monetary incentive that Square might have to allow his use.)
That aside, there are benefits to having a character like Sora. While
KH3 isn't coming to Switch, it could help them get older
KH games re-released on it, just as
FFVII,
FFIX,
FFX, and
FFX-2 were announced to be coming to the Switch in September. It's also a show of good faith towards Square that Nintendo isn't just prioritizing their own gain, and helps solidify the relationship between the two companies to prevent another fallout from happening in the future. However, that definitely doesn't make Sora a "lock", or any other SE character. All it means is that there would be more incentive to add them than Geno.