The first 4G pipeline to have an English accent, EE's variant of the Samsung Galaxy S III not only comes with 4G, but also has Jelly Bean installed out of the box. If you live in one of the 16 U.K. cities where EE has service, you don't have to wait for the update.
With the news coming directly from Sammy, you might expect to see SIM-free models get the update first. This makes sense since each carrier has to test the update to make sure it is compatible with its network. Hey, you didn't think that it was just the carriers in the states that did something like that, did you?
So what about the update for other parts of the world? There have been a number of leaks that didn't pan out including one that called for a late August update for the international version of the phone. To avoid disappointment, your best bet is to wait for an official confirmation from Samsung or your carrier.
source: CNET (UK)