World map is changing gradually, because of Plate tectonics. If East Africa is geographically isolated from African Mainland, ecosystems in East africa will also be isolated from those of African Mainland. It will let East African animals or plants unique like Madagascar.
The biggest question I have is that the separated East Africa will be treated as island or continent?
If it's an island, it will be the biggest island in the world. If it's a continent, it will be the smallest continent. It's fun.