That number just isn't very big. And while anything's possible, there's no reason to believe that Windows Phone 7 is suddenly going to take off.
Why not? Because there simply aren't many reasons for anyone to buy a Windows Phone instead of an iPhone or an Android device.
The OS is nice enough, and is arguably prettier than Android. But there just aren't many feature, design, or app advantages that most people would care about. There isn't a price advantage. There isn't a huge enterprise play here. There may not be a tablet play, if Microsoft favors regular Windows 7 for "slates."
And unlike Apple and Google, Microsoft has no brand cachet. No one's going to buy a hardware gadget because it says Windows on it, though they clearly do for Apple.