Yeah and considering the iPad gpu already has fillrate issues at 1024x768, quadrupling the number of pixels seems unreasonable.
Tegra2 is technically a better solution but with all the A4 hype it would be tough for Apple to switch to Nvidia.
Given all this, the iPad2 is more likely to be an modest upgrade with cameras and SGX540 at the best. Or a little more wilder guess would be Cortex-A9 based A-5 and SGX540.
Also, the scaling would be awkward, because it isn't a multiple.
I don't think so, that's not how Jobs leads Apple. If you didn't see the iPhone's resolution change until the doubling in the iPhone 4, you won't see any different on the iPad.