There are trends in both directions, toward government at levels beyond traditional nation-states (this is particularly visible in European institutions and things like the International Criminal Court, a permanent international court with jurisdiction over persons rather than nations), and toward smaller nation-states. Its not hard to imagine an end state where a narrow range of basic functions were handled by a world government (or a collection of function-specific, separately-constituted, global institutions), but where the unit below that was a set of governments (which might be characterized as "national") over regions smaller than today's nation-states (at least, the medium-to-large nation-states of today.)