The number of national entities is growing. Europe alone has 50 percent more countries than it had some 40 years ago. Many more potentially new nations are waiting in the wings. As we write, Catalonia is considering seceding from Spain. Kurdistan may split from Iraq (and later possibly from Turkey and Iran). Scotland is likely to try again to separate from the United Kingdom. Quebec, once close to leaving Canada, may revisit that. Belgium may split into a Flemish and a Francophone state, and on and on.
While we may not return to the period of small city kingdoms, the end of the nation state is nowhere to be seen.
It is a safe bet that we will see more countries a generation from now than we have today.