No, because the chip is ARM and therefore can only run operating systems that have been ported to ARM (this does, however, include various linux distributions).

from other news reports it appears the A4 is just an Arm processor.

It would kinda have to be to run random pre-existing iPhone apps.

It could have an ARM emulator, but I doubt that's the case.

i'd love to see a vmware/parallels app for the iPad. imagine being able to run os x/windows/linux on this thing.

It'd have to do machine-code translation, and so would be slow as hell. Try running windows in qemu some time to see what I mean.

To be fair, qemu is appallingly slow. Windows in Microsoft's Virtual PC for Mac (on Power PC macs) was several orders of magnitude moe performant.

Machine-code translation can be done well, but that still doesn't mean trying to pack a desktop OS onto a mobile platform is going to be a good idea.