The domain PokemonGray.com has been registered by Melbourne IT DBS, suggesting an enhanced version of Pokemon Black/White is on the way.
Melbourne IT DBS is the same company which registered the Pokemon Black and White domain.
History suggests Nintendo will follow a two version release with a single, enhanced version - Pokemon Red/Blue was succeeded by Yellow, and Pokemon Diamond/Pearl was followed by Platinum.
Given that the third release is typically an enhanced version of what came before, it could be that Nintendo will push Pokemon Gray to the Nintendo 3DS, in an effort to further entice consumers to its newest handheld.
Via Nintendo Buzz