The new movie featuring Kamen Rider Zi-O and Kamen Rider Build is set to debut this winter.
It was announced earlier that as part of the Heisei Kamen Rider 20 Work Memorial, a new movie titled Kamen Rider Heisei Generations FOREVER will be released on Saturday, December 22, 2018. There is no word currently on the returning cast, although it is expected that the combined casts of Kamen Rider Build and Kamen Rider Zi-O will be the first to officially be announced.
The movie is an extension of the Movie Wars series of films that started in 2009 with Kamen Rider × Kamen Rider W & Decade: Movie War 2010 and has since become a yearly release. In 2016 the series was renamed Heisei Generations, and with that came the release of Kamen Rider Heisei Generations: Dr. Pac-Man vs. Ex-Aid & Ghost with Legend Rider which included former cast members Shunya Shiraishi (Kamen Rider Wizard) and Ryoma Takeuchi (Kamen Rider Drive). Last December’s installment, titled Kamen Rider Heisei Generations Final saw the return of main actors Shun Nishime (Kamen Rider Ghost), Gaku Sano (Kamen Rider Gaim), Sota Fukushi (Kamen Rider Fourze), Shu Watanabe (Kamen Rider OOO) and Ryosuke Miura (Ankh).
Kamen Rider Zi-O will make his on-screen debut with Kamen Rider Build as a cameo in the summer movie Kamen Rider Build The Movie: Be The One, which hits theaters in Japan this weekend. The cast for Kamen Rider Zi-O will be announced this coming week in a press conference on August 7, and the series will debut on September 2.
Source: Toei Official Site