Starting May 1, new apps and app updates submitted to the App Store must be built for iOS devices with Retina display and iPhone apps must also support the 4-inch display on iPhone 5. Learn about preparing your apps by reviewing the iOS Human Interface Guidelines.
I don't have iPhone 5 yet. Is it possible to develop 4-inch app using iPhone 4S and publish it to App Store?
Migrating is not the issue. It is about the possibility to use iPhone 4S to develop 4-inch app.
No, the iPhone 5 has a taller screen. There is no way to test that your app properly supports the taller screen on a device with the shorter screen. You can use the Simulator to verify that your app works with the taller screen. But as always, testing on a real device is always better.
Yes.
What you are not allowed to do is submit an iPhone app that doesn't have a 4-inch default launch image and thus doesn't adopt the full 4-inch screen when running on an iPhone 5. But that doesn't mean you are forced to buy an iPhone 5. All my iPhone apps (except one, that's very old and hasn't been updated in a long time) run natively on the iPhone 5 and look good on it, using the full size of the screen, but I do not own an iPhone 5.
Use the simulator for iPhone 5 testing. Yes, Apple does want you to test on all devices possible before submitting, but lets face it. Not everyone owns an iPhone 4, and an iPhone 5, and an iPhone 4s, and an iPhone 3GS, and and iPad, and an iPad mini... It's ok if you cannot test your app on every device, just use the simulator for the ones you are lacking.
