Apple today issued a new software update for the second-generation Apple TV, moving the software version to 4.2.2 as reported by the device. Apple's servers, however, register the update as a new build of iOS 4.3 carrying a build number of 8F305.
There is no word yet on changes included in the update, as Apple has yet to publish documentation on the new version.
Article Link: Apple Issues New 4.2.2 (iOS 4.3) Update for Apple TV