Pokemon Smash has just finished airing in Japan and Junichi Masuda revealed that two new games are to be released! They are titled Pokemon Black 2 and Pokemon White 2 and will be released in June in Japan, apparently for DS rather than 3DS (though of course they will run on the 3DS). It has also been confirmed they will be out in the Autumn (Fall) in USA/Europe.
The reason for doing two games instead of the usual one is that legendary Pokemon Kyurem has two new forms resembling Reshiram and Zekrom and based on Fire and Electric.
Clik here to view.

Kyurem's two forms that will be present in Pokemon Black 2 and Pokemon White 2
From the limited information we have so far, the two games appear to be sequels to the storyline of Black & White, rather than a simple rehash. Obviously this is breaking news so we will keep updating with more as we get it!