Apparently, Samsung wasn't taking any risks with the Galaxy S III phone as far as being compatible for the future with Android 4.1/Jelly Bean. According to a report over at The Verge, Samsung wasn't 100% sure what the final hardware specs of Jelly Bean would be, so to make sure their new flagship phone stayed "future proof" they upped the RAM to 2GB just to accomodate any eventuality. The source of their info was not able to give them any details of how long it will be before the SGS3 will get Jelly Bean, but since it isn't dramatically different than Ice Cream Sandwich, it is entirely possible that it may not take too long. At least Samsung can be rest-assured that the hardware is more than capable. Kudos to Sammy for being forward thinking.
Source: The Verge