According to Eurogamer, Nintendo's Tegra 2 chipset will apparently be used in the next DS, and it's “not unrealistic” that the handheld will out-grunt the current Nintendo Wii.
The Tegra 2 is set to arrive in 2010, so potentially the next DS could follow in the same year, but this is pure speculation.
Not to be outdone by the impressive sounding Tegra 2, Sony's next-generation PSP will allegedly exceed the performance of the Nvidia chipset 'clock for clock', with its single core SGX543.
It's difficult to dispute the claim without seeing anything in action, so we will just have to wait and see.
Still, it's exciting to imagine experiences from the Wii and Xbox in devices so small. Good old technology.