Windows 8 Apps are pretty small in number compared to Apps for Apple and Android. But they are on the rise, if only slightly. The projection is that they will hit 40,000 for February or March of 2012.
"The number of Windows 8 apps made specifically for the US market now stands at 30,045, according to MetroStore Scanner. Again, that number is about 4,000 more apps in the store compared to January's stats; China still has the largest number of localized Windows 8 apps with 31,067 apps in the Windows Store."
Apps Article here