Current Windows 8 is just like Windows 7. It only boots BIOS/MBR or UEFI/gpt. It will be soon when we start seeing the vendors versions as those will only be UEFI and have the secure boot enabled in UEFI.
I would think Microsoft would still sell Windows 8 as an upgrade to Windows 7 and all those computers do not have UEFI or those that do may not even be installed with UEFI mode. I doubt they will only offer it on secure boot systems, but we have yet to see.