The Lego Batman Movie 2

After the release of the 2017 film The Lego Batman Movie, director Chris McKay announced a sequel to the film was in the works in December 2018, with him returning to direct. The film was set for a release in 2022, but it was cancelled because of the box office bomb of The Lego Movie 2: The Second Part and Will Arnett thought that the film wouldn’t work.

Plot
According to director Chris McKay, the sequel was to be about the Justice League and where Batman was in terms of the Justice League now, and the struggles they were going through, as well as flashing back to how the Justice League came together. It would've also featured Batman and Superman’s relationship, as well as Batman’s relationship to a lot of the other members of the Justice League.

Cast

 * Will Arnett as Bruce Wayne / Batman
 * Channing Tatum as Superman
 * Michael Cera as Dick Grayson / Robin

The rest of the cast is unknown.

Why It Was Cancelled

 * 1) Even though the first film was both critically and commercially successful, which grossed over $300 million against its $80 million budget, both The Lego Ninjago Movie and The Lego Movie 2: The Second Part were box office disappointments, grossing $123 million against a $70 million budget and $192.3 million against a $99 million budget respectively, causing Warner Bros. to end their movie deal with Lego in December 2019. Not only that, but Warner Bros. owns the rights to the characters from DC Comics, thus ending any chances of the sequel happening.
 * 2) Another reason was that Will Arnett told Chris McKay and the producers that he didn’t want a sequel, as he thought that such a sequel would ruin the first film’s formula and success.

Results

 * The Lego Batman Movie 2 was permanently cancelled and the first film is stand-alone.
 * Will Arnett cancelled the sequel after the producers finally agreed with him in June 2019 after The Lego Movie 2: The Second Part bombed at the box office, and then he decided to work with other Hollywood projects.
 * On December 19, 2019, Universal Pictures and The LEGO Group were in talks to sign a five-year exclusive deal to develop new LEGO films, which was finalized on April 23, 2020.