In an interview in London today, Tai Yasue (co-director and game designer on Kingdom Hearts 3 and the Kingdom Hearts 1.5/2.5 HD remasters) told us that nothing was off-limits for the upcoming Square-Enix/Disney crossover including Marvel and Star Wars both of which are acquisitions that Disney has made in the nine years since Kingdom Hearts 2 came out.
Yeah, I cant go into specifics, but theres a LOT of new Disney stuff and we have our plates full, sais Yasue. Theres a lot to consider - were looking at all of Disney, the new ones as well, they have a lot of pull and draw.
We have to come up with a world that has a lot of originality. We want variety in our new Kingdom Hearts, so we dont want too many of one sort of world, that would look the same. For each world there has to be some meaning for it, in the plot; in Birth By Sleep, for instance, in the Cinderella scene, the characters learn something specific by relating to Cinderella. Also, gameplay-wise, is that world something that would make gameplay fun? Theres a lot I cant say, but theres so much to consider.
When I asked whether I could safely infer that that Star Wars and Marvel are not off-limits, Yasue confirmed that they are being considered. Well, yeah. Theyre all under consideration, he said. Nothings off-limits, were considering all of the worlds. There are so many wonderful concepts. Were happy about that, but at the same time its really tough to choose.
http://www.kotaku.co.uk/2014/12/02/marvel-star-wars-limits-kingdom-hearts-3