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Since the beginning of time ... with "beginning of time" being defined as the release of the first Android device

... people have been asking when will update X be released for device Y. Even if you look at Google's official announcements and releases, they don't always (if ever) coincide. Only the Nexus branded phones get the updates directly from Google, so unlocked Android phones get the updates from the phone manufacturer. In your case Samsung, who doesn't have a stellar record for updating phones. If it is a carrier supported phones so those updates come from the carrier after the phone manufacturer releases it to them. It could take quite a while, if it ever is released.
You could always flash a custom rom, if one is available for your device, but that would (usually) prevent you from getting further official releases through official channels. However, if you are rooting and flashing anyway, it's not usually much of a consideration.
I'm sure that's not the answer you wanted.
Make sure you make it over to the
Samsung Galaxy S 4G forum for more information about your phone.