Apple's iOS 7 update officially launches on 18 September, which means Australians may see it in the late hours of this evening. That makes it timely to remind developers that any iOS app which you've already created won't be able to be updated from now on without making it iOS 7 compatible as well.
Apple's developer site confirms that you can't make even a minor change to existing apps without also ensuring compatibility with iOS 7:
New apps and app updates submitted to the App Store should support iOS 7 and be optimised for iOS devices with Retina display. iPhone apps must also support the 4-inch display on iPhone 5.
That policy ensures that apps are updated frequently, but it does make minor app tweaking harder. Then again, in the competitive world of apps, if you're not regularly updating chances are you're falling behind anyway.