Direct from Pokemon.co.jp, we have news that a new Pokemon RPG will see release in Japan at the end of 2010. The headline makes mention of a "completely new series". That, combined with the revelation of Game Freak as the developer and a paragraph at the end that discusses new Pokemon, a new game, and innovation 4 years from the release of Pokemon Diamond and Pearl seem to indicate that this announcement is about Generation V.
The article doesn't give a lot in the way of details, but we do know it will be for the DS, and that it is intended to be released by the end of the year.
This month's Corocoro is also supposed to have some sort of 'surprising announcement,' which may also relate to this announcement.
We'll be sure to be on top of news as it develops, so stay tuned.