User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-24098614-20141124022541/@comment-24098614-20141124023922

I don't think personally it will happen because he is breaking his word about keeping the girls happy because if you kill one of those girls that notion of the story goes off the books because it would mess up the ending of those girls sure it is one girl but it destroys the notion of the Harem being together.

I think he is doing the same when Issei died something shocking and unexpected because the girls are important, and Ravel is part of that Harem and losing her throws off the whole premise of  enjoying any happy life with Issei.