There are several Futures on this wiki, and more to come.
Fire Nation Future
Here, the 100 Year War ends with the Victory of the Fire Nation at the burning of the Earth Kingdom. Each Nation is technically not a Nation, for they are United with the Fire Nation and are therefore, "a country of countries".
In this Future, Energybending never died off and the Energybenders still exist as a seperate Nation in Fusang.
When Amon and the anti-benders receive intelligence of the not-yet-discovered Fusang, they claim it as the sixth Nation, the Amonist State of Fusang. They gradually take over the international bending establishment.
Earth Kingdom Future
When a greedy Earth King seeks to expand the empire, it is now the Earth Kingdom trying to conquer the world, not the Fire Nation. But the difference is they succeed.