New iOS releases always find enterprising users digging through iOS code for evidence of future devices being tested, but Apple has made it a bit more difficult to do so. With the release of iOS 5.1 beta 2, Apple added a slew of fake device codenames to the USBDeviceConfiguration.plist file where new devices under testing would often show up, making it much harder to discern what the company might actually be testing.
It's worth noting that Apple actually added these references in iOS 5.1's first beta, but not to the USBDeviceConfiguration.plist file until beta 2. If you live for every shred of new device evidence you can get your hands on, don't despair — developer chronic notes that there's still evidence around, if you know where to look. We'll see if Apple obscures that resource next.