UEFI and Secure Boot are two different things. We've been having EFI machines forever (look at your nearest Mac for an example); it's just that the EFI standard is maturing into UEFI now and is something that can be reasonably implemented, and also that the legacy BIOS boot mechanism is a sufficiently crappy and '80s way to boot a PC that you couldn't implement Secure Boot on it even if you tried, so the forces that want Secure Boot are designing it as part of UEFI.
Secure Boot is no more an inextricable part of UEFI than, say, cookies are of HTTP. Yes, FTP is a sufficiently crappy and '80s protocol that you can't add cookie support to it, but that doesn't mean we need to go back to FTP to eliminate the threat of tracking cookies.
A good number of machines that have been on the market for months are UEFI with legacy BIOS boot support, and have no idea what Secure Boot is.
In any case, as Matthew mentioned, Secure Boot should be trivially disableable in the BIOS menu (on the one test machine I have, with basically a standard-looking BIOS menu with just a few more knobs, it's as obvious as the option to enable hardware virtualization). The worry is just that that's an additional hoop for people to go through before installing Linux. Anyone competent enough to compile their own kernel will know how to go into their BIOS menu and turn off Secure Boot and turn on hardware virtualization while they're there.