Personally, I think the US will not lose its status as a superpower for another hundred years or so. They may have spikes and declines, but it will remain known as a superpower for a very long time to come due to it's gigantic cultural, economical, military, and governmental influence it has on the world. They make the old British empire look like wusses, and the Brits made the old Roman empire look like wusses. This is just a time of decline due to reactions of the events of 9/11 which was the reason that the American economy plumeted shortly after. I'll give the Americans 150 more years of superpower, followed by some 350 years as being a normal world power, followed by 500 years of being around as a nation, and maybe 1000 more years of being a civilization before it is finally assimilated into another civilization and/or nation. Unless, of course, the world ends within this time period. I get my predictions from history. I look at the Romans, Byzantines, Ottomans, Germans (Holy Roman Empire), Britain, and see that they held onto power for a very long time, and lasted for even longer. The Holy Roman Empire is no longer around today, but the Brits still are. Rome lasted for more than a thousand years, it's power for more than half of that. Sure the US may change, both landwise, and culturally wise, but I still believe it will hold onto power for some time to come.