It was supposed to premier this Fall Season
Level-5 has announced that the newest season of Inazuma Eleven has been delayed to the Spring 2018 season. Originally it was supposed to come in Summer, then it got delayed to fall; and now to Spring.
At the same time the event “Inazuma Eleven Dai Fukkatsu-san” will be delayed until September. In such event a new chapter of the anime will be presented. This chapter will be a tie-in between the originals eries and the Ares no Tenbin.
The Story of Ares no Tenbin it is located after the events of the first season; but on a parallel universe since different events happened.
Via: Crunchyroll Latin América (Spanish)