win 8 will have arm support - win 7 doesnt have that. However im not sure about the specific requirements for arm based hardware to run win8.
It will later on in the beta process, but it might take a new device to run it. (due to hardware requirements).
The leaked builds will not work because they have only been x86 and amd64 builds. Once there is an arm build available, then maybe yes. Although, getting working drivers could be tricky.
You hit the nail on the head, drivers WILL BE the tricky part, because I get enough trouble getting debian to work on android devices because of drivers...I could imagine Win8!