Ever since the word broke that Microsoft was replacing "Metro" due to legalities, the world of Microsoft design has been a bit difficult to communicate. It was simple before. We had a name for the design style that has dramatically changed the face of Microsoft.com and the Xbox dashboard. It was easy to describe how the same design style could be applied now to Windows Phone and Windows 8 because there was a common name attached to it. That was all gone in a flash when we learned that Microsoft was no longer using the term "Metro".
What ensued after this was a lot of postulating as to what the new name would be. "Modern UI" was probably the term with the widest amount of agreement. I'm even guilty of jumping on this particular bandwagon. Truth be told though, Microsoft never told us what to call this thing and everything was just guesswork. I had heard since then that "Modern UI" was not the term. In fact, Microsoft does use the term "modern apps," but this refers to apps with a cloud connected focus instead of any particular design style. I'm happy to note today though that the speculation can come to an end.
Microsoft Design Style - the real new "Metro"
I have confirmation from Microsoft employees very close to the matter that "Microsoft Design Style" is the term that should be used to refer to the design style used on Xbox, Microsoft.com, Zune, Windows Phone, and Windows 8. The distinction here is that this describes the whole design style much in the same way "Metro" did previously. When referring specifically to the Windows 8 ecosystem, we can say we are building "Windows Store Apps" using the "new Windows UI" which was developed using the "Microsoft Design Style." Where I might have said "Metro Design Principles" before, I can translate that to "Microsoft Design Principles."
I will be using this term going forward as well as updating references in my Windows 8 design series and book.
Update: Here's some proof of the usage on Microsoft web properties describing Windows Store app design: http://msdn.microsoft.com/library/windows/apps/hh464920.aspx