Apple has laid down the law on new app development. All new apps must be created with the latest Xcode software, and must conform to the design language of iOS 7.
In an announcement on its developer website, Apple has mandated that all new apps must be built with the latest version of its Xcode development software, and must be designed in accordance with the latest iOS Human Interface Guidelines for iOS 7. The same mandate applies to all updates applied to existing apps. Failure to comply with the announcement may see updates or new apps rejected from the App Store.
Apple is pushing hard for consistency between its iOS home screen interface, in-house apps, and the third-party apps from developers available on the App Store; this announcement is a sign that the shift in design is not happening as quickly as it would have liked, three months since the launch of iOS 7. These new guidelines come into effect on February 1, 2014, so developers have ten weeks to revamp their apps to suit the new design if they have not already. It's likely that the change from iOS 6 to iOS 7 design will require significant work in some apps; because of this, more niche or less frequently-updated apps may stop being updated altogether.
Full-screen interactive apps like games and video streaming content will escape the push towards Apple's multilayered, transparency-heavy, highly contrasting iOS 7 design scheme. Simpler apps, like calendars, messaging services and other pieces of software that rely heavily on interface, will require some tweaking.
As well as a new design language, Apple's iOS 7 includes new features like systemwide gestures that may conflict with the usage of some legacy apps. To overcome those problems, Apple has a iOS 7 transition guide for developers.
That guide's advice shows that for some application creators, complying with the new rules may be easy, but for others, it will be more difficult: "If you feel that the current UI and experience of the app is still appropriate, there may be very little to do. On the other hand, if you feel that the app’s personality and user experience should change in order to delight iOS 7 users, you have more work to do."