As I said, the "A4" is a packaging and rebranding of components that are all in the iPhone 3GS. (1) the ARM Cortex A8 CPU, (2) the PowerVR SGX 535 GPU, and (3) 256MB of RAM. I think that the CPU and GPU might have already even been on the same chip in the 3GS. The only difference in design is that the RAM in the A4 is stacked on top of the CPU/GPU package. This has some performance improvement, but not nearly enough to clock the CPU 67% higher. There could also be a die shrink, but again the power savings would not add up to that much.
And yes, the battery found in the Gizmodo 4G iPhone had 16% higher capacity than the one in the 3GS. I still don't see that being enough to get to 1Ghz.