According to the zdnet article linked by recoilednsake:

Update: A spokesperson is now saying the reason for this Metro de-emphasis is not related to any litigation. (I asked if it is related to any kind of copyright dispute that hasn't yet gone to litigation and was told there would be no further comment.)

The spokesperson added:

“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.”