The official Pocket Monsters Diamond and Pearl website has announced that a new ending theme will begin airing in April and that the series will finally be airing in High Definition.

The new ending theme will be sung by Nakagawa Shoko, host of Pokemon Sunday. She is scheduled to have a segment during the March 26th special and the details will be announced during the broadcast, so be sure not to miss it!

On Shoko Nakagawa's blog, she announced that the new ending theme would be called: 「もえよギザみみピチュー」 (Burn with Ambition, Notch-Eared Pichu)

Source: http://blog.excite.co.jp/shokotan/