It will be set after the events of the second season
A movie based on Chuunibyou demo ko gai Shitai!, which will have the surname of “ Take on Me”has been announced and a Teaser trailer has been uploaded, which you can see bellow:
Anime News Network describes the movie film as follows:
“In the film, Rikka is now a third-year student, but she still has “chunibyo” syndrome. University entrance exams loom on the horizon, and it’s spring break, and Yūta and Rikka are together as usual. One day, Rikka’s older sister Tōka declares that she’s going to take Rikka to Italy with her, as Tōka is moving to Italy for work and she thinks they should move together as a family. Yūta understands Tōka’s opinion, but thinks that at this rate he and Rikka will be separated. Shinka and the other members suggest that Yūta and Rikka should “elope,” and thus sets the stage for Yūta and Rikka’s travels throughout Japan in their escape drama.”
Tatsuya Ishihara is directing the movie at Kyoto animation; Jukki Hanada is writting the script.
The Movie will premier on January 2018.
Via: Crunchyroll Forums