In short, no. The secure boot is essentially optional from what I've seen so far; put Windows 8 on any old motherboard and it should work.
The whole reason this has come about is due to the vulnerability of people faking BIOS IDs and manufacturers on startup, allowing auto-authentication of pirate copies of Windows Vista and 7. In order for this auto-authentication to work in Windows 8 on a shipped bundle, secure boot will need to be activated. After the initial secure boot and activation, hopefully it can be turned off and allow more open access on OEM machines. (If it doesn't, then we have a problem.)