Peter Bright, Ars Technica:
From now on, the new terminology that Microsoft is using is “Windows 8-style UI” when talking about Windows 8 applications, and “New User Interface” when talking about the company’s full product line-up.
Turns Out™ it was just a code name:
We have used ‘Metro style’ as a code name during the product development cycle across many of our product lines. As we get closer to launch and transition from industry dialog to a broad consumer dialog we will use our commercial names.