Starting February 1, new apps and app updates submitted to the App Store must be built with the latest version of Xcode 5 and must be optimized for iOS 7. Learn more about preparing your apps by reviewing the iOS Human Interface Guidelines.The new rule goes into effect on February 1, 2014 and means that any apps built on older versions of Xcode or non-iOS 7 optimized apps will be rejected from the App Store.
In addition, this also applies to app updates, providing some inspiration for developers to update their developer tools and optimize their apps for iOS 7 as the updates will be rejected otherwise. Optimizing an app for iOS 7 does not necessarily mean it needs to look different, but that the underlying construction of the app must be optimized for the new OS.
Earlier this month, Apple's App Store usage numbers indicated that iOS 7 had been installed on 74 percent of devices connected to the App Store. The new rule indicates Apple is eager to get developers to take advantage of iOS 7's high adoption rate and make their apps compatible with it to ensure higher user satisfaction.