Yes, but there's clearly a connection to Super Mario Bros. as the name "Super Smash Bros." is clearly derived from "Super Mario Bros.," as Mario is the face of Nintendo.
Likewise, Kingdom Hearts is a Disney spin-off, but Mickey is the face of Disney, which is clearly referenced right on the Keyblade.
Disney may license out Sora to Square Enix, but Sora is owned by Disney, putting him in with Mickey, Donald, and Goofy, not Final Fantasy.
I really don't want to have this argument for the thousandth time, but since Sora will never be in Smash, the speculation will likewise never die.