Yep, no OEM is being forced to do this, and Windows 8 will run quite happily on non-UEFI hardware... But the major manufacturers will want the Windows 8 logo on their machines - they have wanted Microsoft approval since Windows 95 days - and will probably quite happily make these changes voluntarily. If the Redhat guys are correct and it isn't made a user-changeable option, it will effectively mean Linux or anything else can't be run on that machine.
I can't see motherboard manufacturers going down this route though, or at least not having an alternative BIOS option to download. But as it is currently, it's nice to stick a lightweight Linux distro on an old Dell machine to get a few more years of life out of it, and it would be a shame if all those computers just went to landfill instead...