Pokémon: Diamond & Pearl, the show based on the previous Pokémon games, Diamond and Pearl, returns with a two-part special which will air on February 3!
The Hikari - Aratanaru Tabidachi! and Nibi Gym - Shijō Saidai no Kiki! episodes will depict the stories of Hikari/Dawn and Takeshi/Brock after their journey with Satoshi/Ash ended in which Satoshi ended up going in Isshu and met Iris and Dento along the way.
The said anime ended last September with Pokémon: Best Wishes! took its place that same month to coincide with the Fall debut of the Pokémon: Black and White games in Japan.
Source: 4Gamer.net via ANN