User blog comment:B214/Question and Answers 2/@comment-71.108.89.172-20140203083513/@comment-1359322-20140203083902

The story after Volume 19 would probably be Issei and the other officially moving to their third year but then again, it could be like JJJ said, the author might extend the story for the 3rd semester.

As to DxD, not all members will make appearance, only some will make appearance along with the ORC.

Others is all unknown at the moment.