Highschool DxD season 3?
I also just finished High School DxD New, and after doing some "research," and based off of what happens with all animes, a new season is based on three things. One, how well it sells. If it sells poorly, why bother to make another season? Two, how popular it is. If the audience finds it intriguing and wants more, it might push the studio to make another season. Three, how the studio and director feel like doing. Hey, the ultimate decision lies with them! So even though High School DxD New's Episode 12 hinted a lot of things that could be progressed into another season and the fact that the light novels are still ongoing, the power to make another season really depends on the director and the studio, and all the people who really are in charge of High School DxD. So all we can do now, is just pray everyday for another season! :D