Fresh instances that reference "J2" hardware in Apple's latest iOS 5.1 source code have been discovered. iMore published details of its findings alongside additional mentions of a J1 device, both are thought to be codenames for two prototype tablets that Apple is currently testing. A DigiTimes report in November suggested that the J1 and J2 include 2048x1536 displays, and references to the codenames were discovered in the original iOS 5 firmware.
iOS 5.1 beta 3 also includes mentions of Facebook. It's not clear whether this is simply legacy code or a hint that Apple could be closer to integrating Facebook into the core operating system. There's been persistent rumors that iOS will include Facebook integration, but no solid proof that it's under development. Apple opted to include Twitter integration in iOS 5, a move that tripled the signup rate from iOS devices. We shouldn't have to wait too long for the answers to these questions, the iPad 3 has reportedly gone into production ahead of a planned March debut.