When that incentive disappears, as it will, what then? There is no way in hell the middle east can defend against Iranian aggression without other people doing it for them. And it's not just the middle east. The consequences of isolationism will lower enormously. Why won't rich countries just lock the border and dig in?
We're not even that far removed from finding out what will happen, it's only about 7 years away. I'd love some early warning though.