The funny thing is that Google will probably do a better job of the 'mashup of flat boxes' trend than Microsoft. Google's UX team has become amazing in the last couple of years. Their new design documentation is worth looking at.
Regardless of if its a copy or not, or what your views on Google may be, they have some very talented designers on their books these days.
Interesting how people always cheer for the design and "looks" and completely ignore usability.
Also interesting to watch how all these new concepts fail. See Windows 8. The end result will be that Windows 8.1 + 1 will re-introduce the start menu. My guess was that Google would be smart enough to learn from such mistakes. Apparently not.