It has been stated that characters from the Yo-Kai Watch Shadowside series will make an appearance, but whether Yo-Kai Watch 4 is the previously announced Shadowside game or will be similar to previous entries is currently unknown.
Level-5 CEO Akihiro Hino added that the game’s content will be enhanced and that it will include features that surprise everyone.
Yo-Kai Watch 3: Sukiyaki, an updated version of both Yo-Kai Watch 3: Sushi and Yo-Kai Watch 3: Tempura, was the last mainline Yo-Kai Watch game to release in Japan. No version of Yo-Kai Watch 3 has been announced for release outside of Japan yet, although all prior mainline games have received a Western release, and we may see an announcement in the near future.
Yo-Kai Watch 4 will launch on Nintendo Switch in Japan in 2018. The game has not yet been confirmed for release outside of Japan. Stick with GameSkinny for more information as it develops.