Well, theres the LG Optimus X2 sporting the new Tegra CPU which has already been released in Korea.
In terms of battery life dual core CPUs are supposed to be better as CPUs drain power depending on the processing speed they use. So dual core means distributing the load on two CPUs which have a lower workload. Also Tegra 2 is 40nm as opposed to the Snapdragon and Hummingbird CPUs which are 65nm and eat up more juice.
There are no Apps that support Dual core yet. So it won't be able to truly benefit the power distribution there.
On My Nexus S 20 mins of AngryBird equates to 30% battery Life.
On the Tegra it will not use the two Processors to balance the load, it will use one processor for the game and one processor for the background apps Running, in Effect Where I am seeing 30% battery loss I may see alot more on the Tegra.
Not to forget the GPU on the Tegra is a lot more Powerful and in that sense will be hungrier.
Here is an Article about the Battery on the LG
"All this power does come at something of a price however and that is battery life. Like the HTC Desire HD, this is a hungry phone. Leave it alone and it will chug along happily for about a day, but when we stepped out of the office we found that the Optimus 2X didn’t make it through the day. Yes, we were drawing in data, we shot a little HD video (which does seem to take bites out of the battery) and we were playing with the phone a lot, but you’ll need to keep a charger handy. At least you could have a space battery to swap out if you need to." - Source
It does also mention that it is a initial release and there will be bug fixes and some ironing out left. But you also have to note that as it is the Galaxy S wouldn't last a Day either in the same setting, but it will last longer then the LG on the same tests.
But I don't see a practical phone here, I see more of a geek device.
This will likly add to the Android infamy as a geek Device.
I think they need to invest in better power source to increase the battery life to something more usable.