Where will the U.S. be in 50 years?

Will we still exist? Will we still be an economic or military superpower? Or will we just be the remnants of a once powerful nation? As it is it seems we're in decline from a variety of standpoints, economically, diplomatically, scientifically...we've got a ton of problems coming at us in the next 20 or 30 years and we don't seem to have the political will to face them. So what happens to us?