Pokémon transferred to Pokémon X and Y using the Poké Transporter cannot be sent back to their original games, Nintendo has revealed.
The Poké Transporter is a free app that accompanies the Pokémon Bank and allows users to transfer their Pokémon from Black / White and Black 2 / White 2 to X and Y. However, a new FAQ on the Pokémon website has revealed that once Pokémon are transferred they cannot be sent back.
The Pokémon Bank will cost users an annual fee of $4.99–you can check out all the details here. Pokémon X and Y are set to release October 12 worldwide for Nintendo 3DS.