According to this, several developers working on the next-gen DS have said at GDC it could be announced at E3, with a release later this year.
The article also cites that development kits for it are similar to those for GameCube and Wii, with the Nvidia Tegra chip set to be included as its CPU/GPU compared to ATI's CPU chips for GameCube and Wii.
It also backs up rumours that it has motion controls in some form with an accelerometer. Last month, it was rumoured it would have the controls in a similar form to iPhone.
Shigeru Miyamoto's already confirmed new hardware is on the way, though.
Thanks, Game Informer.