Neither platform is exactly in the majority. Windows 8.x had less than 7 percent active usage share in July, according to NetMarketShare, while Windows Phone 8.x was virtually non-existent at 0.04 percent. This likely won't affect a large swath of developers, especially those that were never interested in submitting apps to the Microsoft Store in the first place. However, Microsoft is using the comparatively short notice to send a clear signal: if you rely on its app portal, you'll have to use its latest operating system to reap the full benefits.