User blog comment:B214/Season 3 confirmed!!!!!!/@comment-24502975-20150306152823/@comment-73.178.133.185-20150307195323

If we base things on the previous two seasons, then odds are that there will be 12 episodes covering volumes 5 and 6. Rossweisse does appear in volume 5, albeit as a background character. However, the fact that she has received a separate profile and is depicted in promo art alongside the rest of the ORC suggests that we might in fact get volume 7. Thinking about it, with V6 brings an end to the "Old Satan Faction" arc while V8/9 begins the "Hero Faction" arc of stories. Volume 7 is a standalone mostly unrelated to the Khaos Brigade. At the same time it completes the Issei's "resolving the Gremory group's personal issues" storyline and completes the Gremory group roster. Thus it kind of makes sense plotwise for them to do Volumes 5-7. The biggest question, imo, is: will they squeeze 3 volumes into 12 episodes, or will they expand the season to 18+ episodes?