Projections about foreign policy in the next five years or whatever are pretty boring. Let's start talking about wildly irresponsible foreign policy projections--like over the next century--because then we can begin to get a feel for whether anything is missing from our models.
Consider how poorly realism has fared over the past century. To observers in 1912, the idea of a global conflict might have been plausible. But that the United Sates would be the world's dominant power, that China would be its principal competitor, and that the rest of the league tables for great-powerdom would be filled out by Russia, Japan, India, and so on would have been sheer lunacy, as would the notion that the greatest threat that Europe faced to its domestic tranquility was the possibility that its currency union was insufficiently deep.
Realism talks a good game, but it is shockingly bad at understanding the nonlinearities of economic growth. Liberalism is hardly better. Our major theories of international relations are not just theories of the middle range, they are largely theories of next week.