I think the interesting thing is that it has stuck, no matter what some German retailer would like. At this stage of the game I don't think MS will be able to distance themselves from the name no matter how hard they try - people are just going to call it Metro regardless. I don't know what happens at that point but I would imagine the copyright becomes unenforcable. After all, when was the last time you got sued for calling your Dyson a Hoover. As long as MS don't use the word in their literature or releases I doubt anyone will be able to do anything about it.