I think if this happened we'd get Disney-related skins coming to the game, meaning more Marvel + Star Wars heroes & villains.
Plus, we'd even get mainstream Disney characters as skins, such as Mickey, Donald, Goofy, and even the whole entire Disney Princess roster, hell even go as far as to have their own gliding animations (i.e. the fairy wings popping out of your currently selected skin)
Even more so, we'd have the Disney Fairies spread out across the Battle Royale map that would provide us challenges/quests (i.e. Iridessa would be hanging at Slurpy Swamp, Rosetta would be hanging at Misty Meadows, Silvermist would be hanging at Sweaty Sands, and Tinker Bell would hang at Weeping Woods. The list goes on.) Pixie Hollow (and even Neverland in general) would become one of the landing spots within the BR map. Maybe we'd see pixie dust in the air while playing.
All in all, Disney would see Fortnite as another cash cow given its target audience, and therefore ram it into the ground with a lotta mtx, and perhaps make everyone quit, like has been the case with GTA 5 & Warzone.
Source: https://www.reddit.com/r/FORTnITE/comments/qk7qr6/what_do_yall_think_would_happen_to_fortnite_if/