I'm 100% confident that Nintendo won't sell itself anytime soon, if ever- especially not to Disney of all companies. Besides, Sora getting in probably had a lot more to do with Square than Disney, as Square are the actual devs of his game. Disney def would have needed to approve it, but I don't think that they would have been very involved in the whole thing. Certainly it wasn't a plan to make the Disney brand explictly prevalent in Smash/Nintendo, cause almost every Disney reference was removed, so I can't see them using this as a gateway to trying to buy.
Plus, now that Disney has their finger in Smash Bros thank's to Sora's inclusion.... I predict that they will attempt to buy out Nintendo. Or in the very least, obtain monopoly rights to produce TV Shows and Movies about Nintendo Brand Characters. Imagine a Zelda TV show... but it is actually good to a point and Link has a proper voice actor and isn't portrayed as a whiny wuss?
Or a TV show for Metroid?
And IF somehow Disney obtained Nintendo.... we would see A LOT MORE characters added to Smash and references to the Disney Princesses all over Zelda. I can see it now... an Ice Palace Dungoen having Elsa and Anna paintings on the frozen walls. An Olaf helper character. Thor being an easter-egg boss fight?!
I pray Disney doesn't taint Nintendo.