I don't really like the idea of a general Disney (platform) fighter - not because of corporate woes or uneasiness about Darth Vader beating up Pooh, but because "Disney" is such a vague starting point all things considered and as such even an Ultimate-sized roster would likely be super safe and predictable while also leaving out some super important characters. I think it'd be best to restrict it somehow - the new Disney Speedstorm is focusing entirely on the animated canon, certain live action IPs, and Pixar which I think is a good way to go, but personally I'd want a Disney fighter to be based on a single IP that isn't star wars or marvel - The Simpsons, The Muppets, The Incredibles, Toy Story, The Lion King, Lilo & Stitch, Futurama, I can easily imagine fighting game rosters based on all these IPs without any need for guest content.
(i'm not saying i'm opposed to multiversus adding that kind of content down the line, but not having it at launch makes tons of sense)