Illumination was planning a computer-animated adaptation of "The Cat in the Hat" after the success of their "The Lorax" movie. However, that project was ultimately canceled.
Currently, Warner Bros. Pictures Animation is developing a new animated "Cat in the Hat" movie, scheduled to be released on March 6, 2026. This film will feature a voice cast including Bill Hader as The Cat, along with Quinta Brunson, Bowen Yang, Xochitl Gomez, Matt Berry, and Paula Pell.
So, while Illumination had plans for it, they are not the studio making the upcoming "Cat in the Hat" movie.