Preview at WWDC likely in June, followed by September launch.
Apple Obscures Future Device Hints in iOS 5.1 Beta 2 with Fake References
While the references provide essentially no information on the new devices themselves, as they simply appear in the form of "iPhone4,1" for what ultimately became the iPhone 4S as one example, they are carefully watched as hints of what devices Apple is likely to be testing with the software and perhaps how many variations of an upcoming device there might be.
With today's release of iOS 5.1 beta 2, Apple has now taken steps to obscure that information, planting numerous fake references within configuration files typically examined for such evidence.
One file in particular, USBDeviceConfiguration.plist, had formerly listed about two dozen different device variants. As discovered by 9to5Mac's Mark Gurman, that list has now ballooned to well over 100 such entries as Apple has seeded it with dozens of new fake references to such future products as "iPad10,1", "iPhone11,3", "iPod11,1", and "AppleTV8,3".
The change is likely to make it more difficult to detect new additions, as the new entries will serve as placeholders until Apple quietly begins using the software on its latest devices under development.
Update: As noted by @chronic, the change does not shut out examination of the evidence entirely, as unaltered listings are still visible in other locations. Apple also apparently began adding the fake references in the first iOS 5.1 beta, but only with beta 2 did they make it into the closely-watched USBDeviceConfiguration.plist file.