Apple has let slip a reference to an important iPhone OS announcement, multiple sources confirm. People signing up for the iPhone Developer Program in the past day have noticed an oddity in the service's licensing agreement. Rather than showing a proper set of legal disclaimers, the agreement containts the text "Place holder Agreement - Need to update this for the 27th launch," followed by "Rev. 01-27-10."

The text is a solid indication that Apple will make some form of iPhone OS announcement today, either to premiere or launch iPhone 3.2 or 4.0. Both versions of the OS have been spotted online in recent months, though v3.2 only recently, which given its status as a minor update may suggest it will be ready for download in the near future. Some new version of the iPhone OS is expected to support Apple's impending tablet, which should be revealed at 10AM Pacific time, or 1PM Eastern.