The risk for Apple now is that the OS redesign disrupts its own user-base, so here’s one sign of how Apple is managing the change: it’s updated the App Store to offer a prompt to iOS devices that aren’t compatible with the latest version/s of iOS enabling them to download the “last compatible version” of the app. iOS 7 will be pushed out to the majority of iOS devices — becoming available for general download, beginning September 18 — but the iPhone 3GS won’t be able to get it, nor will the first-gen iPad. While the app compatibility prompt takes care of the owners of those older iOS devices, who would otherwise be getting left behind by the move to iOS 7. The “last compatible” app prompt may be about reassuring developers as much as users, though. While users aren’t being railroaded by Apple onto a version of iOS they may not feel ready for yet, developers get the reassurance that there won’t be a risk of their apps only reaching a sub-set of iOS users who are comfortable about upgrading to iOS 7 right away — giving them an incentive to work on iOS 7 app updates without worrying about whether their users are going to be there yet or not. (Albeit there may be more work required for developers to maintain older versions of their app, in addition to a big iOS 7 update).