Seems a bit odd though to keep the biggest name in gaming, literally, a secret all the way up to release but also happily flaunt Sonic in their ads and Bowser in the previous movies ads though, eh? I think Disney and Nintendo could be working on something together, especially considering that music is randomly playing there but something tells me it ain't Ralph. And Universal is working on a Mario movie and WB is working on the Pikachu movie so why in god's name would they have Mario Kart music in Disneyland if it's not for Mario Kart.The only thing that hurts this arguement is that people in Disney Parks have heard a remixed version of Mario Kart in EPCOT at the Wreck it Ralph 2 exhibit. Disney would know that Nintendo would immediately pounce on them for using music they weren't licensed to use. So its most likely that a Mario reference is appearing in the movie somehow. Especially since its a remade version of the Mario Kart track that you can't find anywhere else. This means Disney most likely remade the song.
I agree that one person can't speak for the whole company, but it definitely helps he is the Vice President of Disney Japan. And agree Nomura wouldn't just do whatever he wanted without consulting Disney. However if we take into the fact that Nintendo and Disney are working together in Wreck It Ralph 2 then the possibility of Sora opens up quite a bit.
I actually have a crazy theory about this actually. That they ARE keeping it a surprise until the very end where they replace Sugar Rush with Mario Kart and Vanellope finds her home there after her game was shut down but I'm not really sure how realistic that is.
I do think Sora has an exceptionally better chance if Nintendo and Disney are already working together though. Fingers crossed.