High School DxD returns with the 4th season and new information was announced during the Fantasia Bunko Festival 2017. The title of the new anime series is High School DxD Hero it will premiere in 2018. During the event, the first promotional video and the first visual of the series were also revealed. 

The first visual of High School DxD Hero: 

Yoshifumi Sueda (Rail Wars !, Gosick, MAOYU, So, I Cannot Play H!) is the director of the series, while Kenji Konuta (Blood Lad, Servamp, Library War) is in charge of the series composition. Makoto Uno (The Qwaser of Stigmata, Rail Wars!, Love Hina) is designing the characters, while the production will be held by Passione (Haitai Nanafa, Hinako Note, Rail Wars!).

Ichiei Ishibumi and Miyama-Zero's High school DxD light novel series launched in 2008, and three television anime series have been based on its story. The first series premiered in 2012, while the second season titled High School DxD New followed in 2013. The third season, High School DxD BorN, premiered in April 2015.

Source: animenewsnetwork.com