It was revealed in the final episode of the third season of the anime BanG Dream! that the franchise will receive three films in the next two years.
Therefore, the first two films, titled BanG Dream! Episode of Roselia I: Yakusoku and BanG Dream! Episode of Roselia II: Song I am, are planned for release in Japanese theaters in 2021, and BanG Dream! Poppin' Dream! is planned for 2022. Additionally, the franchise's YouTube channel posted a video announcing the films.
Furthermore, the chief director for all three films will be Koudai Kakimoto, who also directed the second and third seasons of the anime. Atsushi Mimura (CG supervisor for the third season of the anime) will direct Episode of Roselia, and Masanori Uetaka, who provided the storyboards and directed some episodes of the series, will direct Poppin' Dream!.
Source: ANN