Just hear this out.
Remember, no one ever planned for what to do if the Soviet Union were to declare bankruptcy and go out of business. We never considered that and didn't know what to do when peace broke out. If one had written in a blog somewhere in 1987 that Communist Russia would fall without a war, what would the thread partners have said? 'Capitalism' 'won'.
Supposing the Koran were to be indisputably contradicted, shown to all to be in error, and thoroughly rejected as true, what would the current faithful do? What is the closest thing to Islam? Christian or not, one can see the points of convergence of these two faiths. Moving from Mohammed to the Son of Man is almost logical.
Anyway, what a world it would be! What ideas are there about how that world would look?