If an app update after submitted after July doesn’t meet these requirements it will be rejected from the App Store.
Today Apple shared some free design resources for iOS developers with an update to its iOS Human Interface Guidelines (via 9to5Mac). The resources include UI and template materials to make it easier to design iOS apps. Apple says the design resources are “comprehensive and accurately depict the full range of UIKit controls, views and glyphs available to developers using the iOS SDK.” The files are available in Sketch and Photoshop formats. This is a change from the Sketch-only files in the past. Interestingly, both light and dark UI elements are given. It adds a small amount of fuel to the fire for a rumored Dark Mode.