i agree with archangel's post. i'm checking out the newest episode at the moment, and there's some pretty good shots of locke's group near the beginning. we see locke, sawyer, hurley, ben, claire and her child, roussou and her daughter, and her daughter's boyfriend, with a spattering of extras.
as desmond has been a key figure and probably wouldn't be hidden in the back with the extras, we can safely assume he hasn't gone with locke. he sure doesn't play a key role in the new episode, though. let's see some mo' premonitions, des! where's the booze when you need it?