Boy Genius Report, the website of the popular Engadget blogger, posted an excerpt from their server visitor log that showed browsers claiming to be using the "iPhone OS 4_0" and "iPhone OS 3_1_3" operating systems accessing the site. Observers have seized on this as evidence that a new OS revisions are being tested on the Internet, though the log entries are not in themselves proof that these systems exist.
Just a few weeks ago, an iPhone carrying the hardware designation "3,1" was spotted by Pandav, the developers of iBart, on the San Francisco Bay Area's rapid transit system. The combination on new hardware codes and software user agents has encouraged the spread of talk about new releases.