Also that the story was about old characters getting revenge on Mickey.
A lot of people are speculating that the main villain could be Oswald the Rabbit. For anyone that doesn't know, Oswald was Walt Disneys original creation that he made before Mickey Mouse. Since he made it while working for Universal Studios, Universal owned the rights to the character. It wasn't until 2006, that Disney would get the right to Oswald the Rabbit back from Universal. They traded sportscaster Al Michaels to NBC, in order to get the rights to Oswald back.
So considering how Disney really wanted Oswald back and he was Walt Disney's original creation before Mickey, I'd put good money on him being the final boss. Hey maybe he'll merge together with Walt Disney's frozen head and become Giga Oswald the Walt Rabbit.