Various beta releases of iOS 5.1 have already given us a number of clues as to the possible plans of Apple, including the inevitable things like releasing the iPad 3 and iPhone 5, to the plausible with the code saying that those next-gen devices will have quad-core processors, to now the possible with news of Siri.
Of course, this could just be a bug that those users are seeing this disclaimer. It would seem odd that iPhone 4 and iPad 2 users wouldn't be in the mix, but it could be the real deal. Only time will tell.
source: Cult of Mac