If I'm honest Sora I believe is the final DLC pick. Let's get something clear right here and right NOW. Sora is owned by Disney. Just like how for Banjo we see the credits say Microsoft and NOT Rare. Seriously look up Banjo's credits it says Microsoft.
Anyway, Disney is the big honcho here so Sora is a Disney rep even if all his games were developed by Squaresoft. So Sora's credit should read Disney simply because that's who owns him. I'm sure Square makes nice money via Kingdom Hearts games, but the owner is Disney.
The other factor to consider is Hashimoto (Kingdom Hearts producer) is not ignorant. He KNOWS customers want to see Sora in Smash. Another thing is the famous Smash player ZeRo getting some face time with Sakurai and he also hinted at wanting Sora so it's safe to say that Sakurai personally is aware of this character's popularity.
All these factors combined make me believe that Sora is the final Fighter's Pass character. Dragon Quest does not deconfirm anything for Sora. To reiterate Square Enix's properties have never been competition for Sora. This isn't like how we'll never see Goemon and Klonoa or hell even Dimentio in Smash. So I think things are looking good for Sora.