@"one BIOS to rule them all"
You do know that outside the Wintel world, EFI (or its UEFI successor) has replaced BIOSes now, as on Macs, right?
Did you also know that UEFI and ARM already go together?
http://www.arm.com/community/software-enablement/uefi.php
As others have already said, if Windows running on ARM has any worthwhile impact, it will be because it gets ARM systems to market with a consistent underlying hardware (and firmware) platform for ARM system builders to base their efforts on. There are lots of ARM chips and boxes around now, many of them will run a Linux, but they're not exactly a consistent underlying hardware and firmware platform.
Mind you, the Advanced RISC Computing consortium (Alpha/MIPS/PPC) had such a common platform spec, and boxes to match, but back then it didn't do them much good.
We'll find out soon enough.
@Todd
Otellini: "there will never be a 64bit XEON"
Tee hee. See also "Itanium is the answer for industry standard 64bit computing".
Or, as per the title of one of Todd's relatively recent LPs: Liars.
I preferred that old track of yours, "Sons of IA64" though.