updated 07:40 pm EDT, Tue May 15, 2012
Traces of new versions appear just before releases
An unnamed app developer informed 9to5Mac earlier today that users accessing its software had been identified as running iOS 6 by analytics. Other unidentified developers polled have also been seeing the hallmarks of the new iOS version since late April. Versions of iOS 5 appeared prior to the 2011 Apple World Wide Developer's Conference in the same manner.
If enabled in an application, iOS applications can send usage data to developers. This data is typically used for application improvement, and to track metrics of users in regards to which device along with which version of the iOS are being used.
It is possible for a jailbroken device to spoof, or fake, an iOS or device revision metric passed to a developer, but this is unlikely as iOS 6 is known to be under active development. Similar metrics appear in developer's logs just prior to operating system patches, and are generally indicative of compatibility testing prior to a release. [via 9to5Mac]