I think some countries are likely going to be continued to be explored in Animal Kingdom. I think India is sort of represented in the Asia part of Animal Kingdom as is parts of sub-suharan africa in Harambe (though obviously there are dozens upon dozens of countries with different cultures there). That being said I would love to see Australia and Madagascar added to Animal Kingdom to represent the various spectacular kinds of animals that are on display in those countries, and there can be authentic restaurants in the area to showcase the cuisines of each nation. Madagascar largely because of the unfortunate status of many of their unique fauna and flora I think could be especially meaningful at Animal Kingdom. A lot of people know very little about it, but this could display why it is so importnat that island continues to flourish, as most of the animals there are not found anywhere else on earth.
If that were to happen, I'd want Egypt, Russia, and Brazil added to the WS. The reason I'm saying those is just because a Egyptian Pyramid, and it's history are fascinating, but Russia is the largest country on the planet, and is not represented. Nothing from the entire continent of South America is there (nor is Australia). The real question comes in what do they want to explore more in Animal Kingdom then in Epcot. For example, I don't see Russia ending up in Animal Kingdom, nor do I see Madagascar as a likely country to be added to Epcot (though that would be cool).
With the Amazon, a strong case could be made for Brazil going to Animal Kingdom, but either way, if Epcot is about representing the world, then two whole continents are being ignored as of now, as well as the largest country on earth. Maybe if Brazil goes to Animal Kingdom, Machu Picchu of Peru could be in WS.