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.
So it looks like from May 1st onwards, any apps submitted or updates will be Retina and iPhone 5 ready.
In a separate announcement, Apple has informed developers apps and app updates that access customer UDIDs will no longer be accepted for approval into the App Store as of May 1st as well. Apple tells debs to “update your apps and servers to associate users with the Vendor or Advertising identifiers introduced in iOS 6.”
In February, Apple introduced App Store short links for developers to promote their apps.