Supposedly, the video above is a leaked official build of Jelly Bean running on a Samsung Galaxy S III. The video is in Spanish, so you might need a friend or family member to translate it for you. Regardless, it seems to confirm all the intel we have received suggesting that Jelly Bean will soon be coming to the Samsung flagship device. Keep in mind, this build also shows Samsung's TouchWiz along with the Jelly Bean build, so that's why it looks a bit different than the Nexus 7.
Source: S3Forums via UnWiredView