User blog comment:CNBA3/Future Filler Arcs (WARNING: ANIME WATCHERS, MANGA SPOILERS!!!)/@comment-112.198.79.220-20140628161225/@comment-7418318-20140629180917

More likely they are going to prevent one from happening.

Whatever story will happen in the filler arc needs to not contradict the manga story and a World War would have too far-reaching consequences and aftermath to fulfill that requirement.