I don't see why linux can't adapt to these boot protection schemes. Self-signed or vendor signed, as long as there's a way to import your key information, what's the issue? Frankly, code signing is a good thing, especially if you can perform it from the ground up.
I understand the anxiety, here, especially given that Sinofsky is not a popular figure and nobody wants to trust any initiative he backs. That having been said, MS (and partners) would be opening themselves up to swift antitrust action again if they were to engage in industrywide attempts to lock out OtherOS.
It's also important to recognize that there are deployments out there where people WOULD like systems where you CAN'T disable secure boot, and have really stringent protections around the boot process. It is unlikely that this type of configuration is one that would be used in the general consumer market; there's too much of a need for boot media and utility software. Imagine not being able to run memcheck or a recovery tool, ever.
Now, really, we need to hear this kind of language from BIOS, mobo, and ready-built systems manufacturers. Overall, an initiative like this is a good thing, but everybody needs to be on the same page. Not foaming at the mouth.