Do you believe the United States (as we know it) will fall in the next 60 years?

A friend of mine and I are having a heated discussion. He is very worried that we will become a second rate country, with massive restrictions/controls on the population. According to him, it will probably either a neo-nazi or Marxist state. He fears that what happened in V for Vendetta will actually happen to the United States.

I personally think we will most certainly change. We may no longer be considered a superpower, but much more then that? I disagree. Not in the next 60 years. What are your thoughts?