I like this. 'metro' is unnecessary jargon, a design language does not need to have a trademark name. Just referring to it as what it is makes a lot more sense.
I have mixed feelings. The Metro UI described one specific portion of the Windows 8 interface, which gives it a use for differentiating between metro-style and old-windows-style. It seemed like good branding. And, one that could be shared across platforms.
Now it's "Window 8 Phone featuring Windows 8-style UI" where the unique Metro branding could have served well.
Then again, I noticed a friend had Windows 8 loaded on his laptop the other day, and he had no idea what I was talking about when I asked how "metro" was
Not quite. Cocoa is really just an Objective-C API, though it's coupled with Aqua through Xcode and recent innovations like AutoLayout, whereby HIG policies are enforced by code. Metro seems to be more than that.