Although we’ve seen a Gingerbread leak already, nothing has been said as to when an actual update would be released for the Samsung Galaxy S. However according to a recent tweet by Three UK it seems, although unspecific, that a release is imminent and may be soon as seen by the image below.
Nothing has been mentioned as far as US variants of the Galaxy S, however most of the ROMs, at least GSM-wise, grab parts from the Galaxy S software. So you will most likely see something custom come your way if this update hits the rollers.
Source: @ThreeUK