I think 4th age won’t have it’s own civilizations

1. Modern nations is not a good option. America transitioning into USA is weird and for certain major nations like China, Russia or Iran I don’t see how they can be represented without controversy. Not just representing them at all, but also their abilities, civics etc.
2. “Fantasy” nations like European Union is also not a good options. Just creating nations on some sort of what if scenario could be big hit-or-miss and it would be a lot harder to create interesting identities for such nations.
3. As some mentioned, 4 country changes is too much and 3 is a sweet spot.
4. If 4th age is a dlc then eventually as other ages get more civs it would feel barebones. And they wouldn’t release dlc’s for a dlc.

I think we might get more focus on government’s since you can really be creative involving future stuff like AI in government. Also you can approach warmongering, nationalism, autocracy and even genocides without pointing fingers at current countries.