Seriously, I'm not aware that any new countries are planned for Epcot at this time.
At various times, Disney announced Spain, Israel, Equatorial Africa (not a country, but a region), Switzerland, and Russia. And Disney has displayed models of a proposed Denmark.
If you can talk some entity into funding a new country at Epcot -- whether that entity is a national government, a rich corporation, or a collection of corporations -- then there will be a new country.
Does anyone on DIS have a $100 million and want to fund a new country at Epcot?