Disney: Bringing like half of their Marvel Roster to Orange Justice dance next to Rick, Batman, Master Chief and Kratos.
Allowing Rare to use Pirate of Caribbean in Sea of Thieves with the Likeness and Sound alike/voice of Johnny Deep even with all of the controversies
Allow Wreck it ralph in Sonic All Star Racing
However Sora in Smash Bros? **** no.
Yes, Disney will license its IPs to essentially anyone who is willing to pay for them. I have no doubt that, in the event Nintendo did or ever does contact them to discuss Sora joining Smash, Disney would (at the very least) be open to the idea on paper and would come to the bargaining table with the intent of making a deal happen.
That doesn't automatically mean they're easy to work with. They still have requirements and conditions that must be met when depicting these characters and, more importantly, Nintendo and Sakurai have to be at least willing to meet them halfway. And no, the fact that they let Marvel characters do a silly dance as a part of a promotion in Fortnite does not mean they are suddenly hyper-liberal with all of their IPs, especially since (IIRC) Marvel does a lot of their licensing for their games directly.
We do not know how Disney would theoretically want their content portrayed in Smash because they currently have no content in Smash and there is no public information on how any meetings between Nintendo and Disney went (in the event they happened). They could demand Mickey appear alongside Sora in Smash, they could demand Mickey never appear in Smash Bros. They could say "Sure, Sora's fine, but you have to include Iron Man as an additional DLC fighter down the line". It's impossible to know exactly what they demand because they're the biggest entertainment company in the world and will often throw around their weight to make sure others are meeting their often fickle demands. This becomes an even bigger factor when discussions about Kingdom Hearts in Smash are basically guaranteed sooner or later to hit the subject of Mickey Mouse, their mascot whom they are willing to protect to the point of spending hundreds of millions of dollars to change the federal law of the ****ing United States to ensure the gravy train keeps going.
This becomes even more complicated when you factor in the other party in this situation. Sakurai can and has put his foot down when corporate interests butt heads with his creative vision. "I have an opportunity to use one of the most famous characters in gaming, period, but I may have to use his recent redesign? **** that, give me the original or give me nothing". "I have to change the design of one of SNK's most famous characters and one of the most female fighting game characters of all time? Yeah, no, Mai's just not showing up and I'm publicly going to put that on CERO's head".
There is no issue where Sakurai has drawn a more clear line in the sand than that of non-video games characters. They will never happen while he's still connected to the series. Like it or not, Disney is a part of Kingdom Hearts' identity.
Has Disney's presence decreased as the series has gone on? Yes. Does Kingdom Hearts have more than enough original content to fill a Challenger Pack? Absolutely. Do these facts alone guarantee or even make it likely that Disney would be fine with having no references to other, outside IPs in a Challenger Pack? No, because if Disney says "I don't care if Mickey isn't allowed in Smash because of some arbitrary internal rule you have. We see the attention Smash reveals get and we want some of that for our mascot who has traditionally struggled with the demographics that Smash Bros. attracts. No Mickey, no Sora", then that's that. If Sakurai's not willing to make exceptions for PAC-Man at the bargaining table, then I really don't see him doing so with Sora, especially when Disney could be asking for a lot more than that a specific design is used.
Sora would be very cool in Smash. Sora has a lot of pros when it comes to Smash. Sora could realistically be added to Smash Bros. either as a DLC character now or a newcomer next game. There's no ambiguity that he's a viable option. However, I'm honestly sick and tired of people acting like having to negotiate with the behemoth that is Disney and/or finding a mutually agreed-upon answer to tackling Kingdom Hearts' licensed elements aren't major roadblocks that could make or break whether or not Sora is included.