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Nomura, as we all know, revels in symbolism in many aspects of the characters and worlds of the game. Considering this, should we be looking for a connection between Sora and Yozora, and thus a possible hint at what's to come?
Sora's name in Japanese means "sky". Yozora (夜空) means "night sky".
I think it's quite possible that whatever the new setting is, it may be something that's used almost a mirror to the world the previous games have taken place in. Not opposites, like the worlds of Light and Dark, but almost a kind of parallel world situation. There were a few interesting things in the movie related to mirrors/reflections and opposing colors/locations, and I think the basis of all of this may be the Sora/Yozora connection.