I swear this has to be one of the most unsatisfying ending of manga history. I mean it literally end in the middle of the story directly at the start of what should be the final arc.
I have to disagree with you there. That "final arc" would, considering their plans, take years and years until they're finally even in a position to go through with it, and even with access to assassins and such, I don't think any mangaka would seriously be able to solve something as complex as the refugee problem, so it's much better to be left open-ended in that regard.