"The iPhone 4 boasts 10 hours of use on Wifi with one charge."
Is that assuming it never connects to anything?
Nope as my iPhone has wifi on all the time (3GS) and it lasts all day, sometimes two days if I do hardly anything with it.
Actively searching for wifi connections and actually staying connected to (and using) a wifi connection are two different drains on the battery. The hardly doing anything with it thing definitely helps battery life too, the DSi can last two days in standby mode only opening it to check the time or play only a few minutes of a game at a time.
The 3DS will have (should be able to have) lots of power and plenty of battery life... And do video out replacing the need for a Wii upgrade, at least for a few more years.
And BnM it was a few posts ago, but having the 3DS pull double duty makes it not just a portable. The 3D screens (from Sharp at least) max out at 4.5" giving Nintendo a lot of space to place hardware. The DSi XL is a fairly large device and if the 3DS is that size or slightly smaller and built on a platform like Tegra 2 in that it would have two CPU's; the stronger one would run the Wii3D software and maybe Nintendo also sells a dock with extra storage space and power cord, and the weaker, less battery draining, but still adequate CPU runs the 3DS software.
It probably won't happen but a man can dream can't he?
Edit: They can show off the 3DS with simulated screens, MS and Sony do it all the time, and then have the journalists report the accuracy of the screens, done right and they will wins over hordes of people.