Apple has posted a warning on their developer news site that they will no longer accept apps that reference the unique device identifier, starting May 1. It writes,
"Starting May 1, the App Store will no longer accept new apps or app updates that access UDIDs. Please update your apps and servers to associate users with the Vendor or Advertising identifiers introduced in iOS 6."
This move follows almost a year after Apple began enforcing the initial deprecation.
In related news, Apple will no longer accept pre-Retina apps starting on May 1. All App Store apps must be built to support iOS devices with Retina displays as well as the iPhone 4" family.