Keep in mind that the reason the PSP's battery only lasts "3-6 hours", is due to its enormous CPU/GPU battery usage, and hefty clock (333 MHz CPU, 160 MHz GPU), relative to the DS (66 + 33 MHz CPUs), and DSi(133 and 66 MHz CPUs).
Like all high-end electronics, the tegra is gets more power hungry at higher clocks. If Nintendo is gunning for more than a PSP-esque battery life, the DS 2 will probably be on par with a GameCube, in terms of performance (the DS being roughly on par with the N64).
Also, if Nintendo announces this in late 2010, you can surely expect it within a year's time. They'd be pretty foolish to announce the successor to a platform earlier than that, given that DS sales will probably drop off considerably after the announcement.
DS 2 == late 2011. On par with GameCube, and probably on par with Apple's next iTouch.
