User blog comment:B214/High School DxD Hero Discussion/@comment-162.252.126.39-20171021163334/@comment-26926813-20171023080753

If 4th season will be succesfull, then will be defenetly a 5th season, because Kadokawa and Ishibumi made a contract with new studio (Passione) for at least 2 season with possible of 3 seasons. And with them Ishibumi said in interview that he planned to ended Heroic Oppai-Dragon Arc with them (not sure if he talking about 2 or 3 seasons).

But they create a opening for not continue the anime if HERO won't be succesfull (they don't made contract with current director for season 5).