A leaked Jelly Bean update was recently discovered on XDA for the T-Mobile Galaxy S III variant. It appears to mirror the recently updated leak of JB for the international version of the SIII. It does come with its fair share of ricks if you plan on giving it whirl though. You need to be running a stock build of T999UVALH2  for starters, which is easy enough to pick up and flash. If you go for the Jelly Bean OTA leak you will most likely lose root and/or your recovery will be over written. Seems like Wi-Fi calling is not function and Google Now is a bit of a hit or miss. There are certainly some other bugs to be found that could make this less than a stable release. On the bright side though, it offers up our developers something to play around with.
Samsung is reportedly going to be pushing the official Jelly bean OTA out to the international Galaxy S III alongside the announcement for the Note 2 on August 29th. The next question will be how long it will take Samsung and the U.S. carriers to get their updates out. Hopefully they should all see Jelly Bean within a few weeks. We will keep our eyes peeled and be watching the live stream of the Samsung Unpacked event where they should announce more details.
If you want to brave the update and see what happens, head over to Luffarjon’s XDA thread for the OTA file. Be sure to read through the comments to see what others have run into or are saying. And as always, you are free to do what you wish but if your phone sprouts legs and tries to take over the world, it’s not our fault.
Source: XDA via Androidpolice