Mickey and Company

Before Treasure Planet was shown in cinemas, Thomas Schumacher, then president of Walt Disney Feature Animation, mentioned the possibilities of having direct-to-video releases for Treasure Planet as well as a television series. He stated that they already had "a story and some storyboards and concepts up and a script for what a sequel to [Treasure Planet] could be," and that they also had a "notion" of what the series would be.

Director Jun Falkenstein and screenwriter Evan Spiliotopoulos began early development on Treasure Planet 2. In the sequel, Jim Hawkins and Kate, his love interest and classmate at the Royal Interstellar Academy, must team with Long John Silver to stop the villainous Ironbeard from freeing the inmates of Botany Bay Prison Asteroid. Willem Dafoe was set to voice Ironbeard. The sequel was canceled when Treasure Planet disappointed at the box office.

Unproduced Disney movies

• Snow White Returns (1938): A sequel to Snow White and the Seven Dwarfs.
• The Wizard of Oz (1939): Originally Walt Disney's follow-up to Snow White and the Seven Dwarfs but the film rights were lost out to Samuel Goldwyn, who originally intended to make it as a standard musical comedy, with Eddie Cantor as his star. However, Goldwyn ended up selling the rights to MGM in 1937.
• Don Quixote (1941): It is about a man named Alonso Quixano (or Quijano), a retired country gentleman nearing 50 years of age, lives in an unnamed section of La Mancha with his niece and a housekeeper. He has become obsessed with books of chivalry, and believes their every word to be true, despite the fact that many of the events in them are clearly impossible. Quixano eventually appears to other people to have lost his mind from little sleep and food and because of so much reading. He decides to become a knight errant, and with his fat, food loving, squire Sancho Panza, sets out on an hilarious misadventure.
• The Tales of Hans Christian Andersen (1943): The film was meant to be a co-production with Samuel Goldwyn, who also wanted to make a film about Andersen's life. It was decided at some point that the part of the film would be shot in live action, with animated segments depicting some of Andersen's tales. These included The Emperor's New Clothes, The Emperor's Nightingale, Through the Picture Frame, The Little Fir-Tree, The Steadfast Tin Soldier and The Little Mermaid.
• Bambi's Children (1943): Sequel to the original Bambi film. This film would have dealt with Bambi's adult life.
• Little Red Riding Hood (1963): This proposed feature was to be an adaptation of Brothers Grimm's tale "Little Red Riding Hood", involving a little girl tries to travel to her Grandmother, but she was raced by a Wolf.
• Goldilocks and the Three Bears (1963): This proposed feature was to be an adaptation of Goldilocks and the Three Bears, involving a little girl who breaks in the Bears' House.
• Hansel and Gretel (1967): This proposed feature was to be an adaptation of Brothers Grimm's tale "Hansel and Gretel", involving a brother and a sister threatened by a cannibalistic witch living deep in the forest in a house constructed of cake and gingerbread.
• Who Discovered Roger Rabbit (1990): The shelved proposed prequel to the 1988 Disney/Amblin film, Who Framed Roger Rabbit. The film, which previously went by the working title, Roger Rabbit Two: The Toon Platoon, was set in 1941 and the Second World War, and would have had Roger Rabbit and Baby Herman going on a journey through the perils of the war in search of Roger's birth mother and birth father, in the midst of the Americas. It also would have been a musical, also would have been a direct-to-video release.
• Sinbad the Sailor (1992): This proposed feature film, itself based on the Arabian Nights tale of the same name, was scrapped after Aladdin was released.
• Swan Lake (1993): Later retooled into The Swan Princess by former Disney animator and animation director Richard Rich, who had been working on and proposed a pitch to Disney about the said film.
• Dumbo II (2001): Disney planned a proposed direct-to-video sequel to Dumbo; it was aborted before it began production, and the development of the film was never revived.
• Hercules II (2001): Disney planned a proposed direct-to-video sequel to Hercules. Hercules is now living in Athens with Megara and their daughter, Hebe. However, when an old friend named Helen is captured by the evil Paris of Troy, Hercules joins the united Greek army as they head out to war; however, this war will create revelations, including Hercules finding an old friend who eventually went missing.
• The Nightmare Before Christmas 2 (2001): At one point, Disney had planned to do a sequel to Tim Burton's The Nightmare Before Christmas, but instead of using traditional stop-motion animation, the sequel would have use computer animation instead. Burton, however, convinced Disney to drop the idea, as he was very protective of Nightmare, and did not want a continuation of Jack Skellington's chronicles outside Halloween World.
• Treasure Planet II (2002): The cancelled direct-to-video sequel to original film. Treasure Planet: The Animated Series was supposed to follow the said sequel.
• Fantasia III (2006): Also known as Fantasia 2006, this would have been the third film installment in the Fantasia series, until the plans were eventually altogether dropped, and proposed segments from that abandoned film was instead produced and released as individual stand-alone Disney animated shorts.
• Mulan III (2006): At one point, a third film in the Mulan film series was planned; like the first sequel this proposed second sequel to Mulan would have ultimately gone direct-to-DVD. The production was eventually canceled.
• Meet the Robinsons: First Date (2007): The canceled direct-to-DVD sequel to Meet the Robinsons. It would have further chronicled Cornelius Robinson's new-found life, as a teenager, growing up, going on his first date.
• Disney's Dwarfs (2007): At one point, Disney was developing a sort-of Lord of the Rings-like franchise series of direct-to-DVD films, that which would chronicled the adventures of the Seven Dwarfs before they met Snow White. The proposed project didn't go through, and the planned resulting series was ultimately canceled.
• Newt (2010): The first canceled proposed project from Disney/Pixar. It would have concerned the exploits of two blue-footed newts, one male and one female, trying to find each other and then bonding themselves, and eventually made to prevent the extinction of their newt race, as well as trying to avoid the need to hate and stop caring about each other in the process. It was planned to be released in 2012.

Source: Wikipedia (You can see more unproduced Disney movies on this link).