I know Gates is incredibly successful, but what makes him think that his success in business and computers makes him qualified to be the authority on what type of world government the planet needs? America is a pretty diverse place, with 300 million citizens, and look at the level of disagreement and political vitriol that exists here. How much more dysfunctional do you think a world government representing 7 billion people would be, where the majority of government on the planet has corruption as a central tenet of its existence? I think it's so unworkable that not only will it never be possible in our lifetime, but it will never be possible PERIOD.
If you have trouble making a stable version of Windows you're in for bigger problems with a global government!