It's a Whole New World We Live In.

After the defeat of Tirek, Instead of receiving a castle; The tree of harmony goes haywire and causes a mass eruption of magic all over not just Equestria but the entire world. Arceus, viewing this decides to help Celestia and the other world leaders to transport their subjects to the Pokémon world. With little to no knowledge of the Pokémon World and the loss of their homes, can the inhabitants of Equus live in harmony with the Pokémon? Or will it end up in utter chaos and war breaks loose.

Basically the reverse version of A New World, a New Way.