Epic Mickey 3 was originally intended to be the final part of the Epic Mickey trilogy.
Warren Spector was asked about creating a trilogy. He said that was what he had in mind. These are some of Warren's exact words: "I don't do anything that isn't extensible. And I will certainly feel that I have not done my job if we can't make other games in this world with these characters. In my head, I've got two more planned."
Warren Spector also says that just because someone plans a trilogy, doesn't mean it will happen in reality. Spector has also confirmed that he had an "idea" for the story of Epic Mickey 3. Spector has stated that the musical bits of Epic Mickey 2: The Power of Two were a "test bed". Depending on the reception, for the next game he would have been going crazy with the musical songs, with Epic Mickey 3 possibly being a full blown musical. Depending on the timing the next game could have seen a potential release on the Next Gen platforms.
On January 29th 2013, it was announced that Junction Point Studios was being closed by Disney. Disney, however, do still have the IP for Epic Mickey, but no plans have been announced, meaning the chances of a sequel are slim. As is the case with many cancelled games petitions have been made by fans, though none have persuaded Disney to select a new developer.
On 30th April 2015, Warren Spector responded to questions regarding the game. He stated that he really wanted to up the multiplayer action and make a truly interactive musical game and make music in the context of a game that no music-game has done yet.  Warren also stated that the third game would have left Wasteland.
Epic Mickey: Power of Illusion is considered as the final part of the trilogy by some, but it's more commonly considered as a spin-off.
A brief teaser was shown at the end of Epic Mickey 2 that shows all the Petes going to Ventureland with a fearful Gremlin Prescott trapped in Big Bad Pete's hand. He then says: "Look at them all, so happy. They ain't even going to know what hit'em!". This showed the possibility of the Petes being the villains of Epic Mickey 3. If you also thin out various areas in the Mad Doctor's Attic in the sequel, you will find costumes that Gremlin Gus and Oswald mention aren't suited for the Mad Doctor. These are in fact costumes that belong to Pete in his various appearances in the cartoons. These hint that the Attic has become the hideout of the Petes, since the area is connected to Ventureland, and the Petes go into the respective projector after the events of the sequel. However, nothing will happen or change if you follow them.
- Epic Mickey' planned as three games by Warren Spector
- Warren Spector Hints At Epic Mickey 3
- Epic Mickey 3 Petition