In a note on its Apple developer website (https://developer.apple.com/news/), Apple tells iOS app developers that it will no longer allow apps to use the unique device identifier or UDID after May 1. Also, all apps must be Retina display ready.
Apple tells developers to “please update your apps and servers to associate users with the Vendor or Advertising identifiers introduced in iOS 6.” For more info go to http://tinyurl.com/a9wqxsu .
Starting May 1, new apps and app updates submitted to the Applel App Store must be built for iOS devices with Retina displays, and iPhone apps must also support the 4-inch display on iPhone 5. Developers can learn about preparing their apps at http://tinyurl.com/6yg25x3 .