iPhone developers required to make all apps work with 3.0 update
Existing, incompatible games may be removed from the App Store
While it makes perfect sense for applications to be compatible once the new firmware has been rolled out to the iPhone public, Apple is also insisting that existing apps will need to work on the new software or they may be pulled from the App Store:
Beginning today, all submissions to the App Store will be reviewed on the latest beta of iPhone OS 3.0. If your app submission is not compatible with iPhone OS 3.0, it will not be approved," reads the memo.
Existing apps in the App Store should already run on iPhone OS 3.0 without modification, but you should test your existing apps with iPhone OS 3.0 to ensure there are no compatibility issues. After iPhone OS 3.0 becomes available to customers, any app that is incompatible with iPhone OS 3.0 may be removed from the App Store.
On potential issue raised that will cause compatibility problems is with any application that uses a confirm/deny dialog (and a great many do), which uses the UIAlertView system thats seen a significant overhaul in 3.0.
A months warning isn't much time for developers to test and prepare any required updates to their applications, but it would appear they don't have much choice in the matter.