Received this from an anonymous source. Take what you will from it.
While attending Yessica Kumala's yearly "end of lost" celebration bash she prepared for Josh, which took place on May 31st at their home in Honolulu, I managed to snag a few tidbits regarding the season 4 opening episode. He was reluctant to tell me anything, and supposedly didn't know anything as he hadn't got the script yet, but after a few drinks he managed to pop a few out. I cant remember the exact words, but the following was roughly what he told me regarding the season 4 opener. This may or may not be true as he says this is what he heared floating around the set as he did his final scenes for the season 3 finale. Firstly, the season will supposedly open with a similar situation as season 1 and 2, however, this time its slightly more obvious. The episode apparently opens from "???" point of view, on the "rescue boat". Secondly, as a fan of Desmond, I asked if he knew how things ended with him. Again, he reminded me that this was just a rumour, but Desmond does not make an appearence in the first episode, however, Penny does. The final tidbit he popped out was about Locke. He had been in talks with Terry O Quinn, and found out that Locke will be a much darker character next season, and apparently knows alot more about the "rescue party" than he is letting on, and that he had previously knew "Cassie?" (one of boat crew) whilst dating Helen (perhaps a fling?). This information may not be much, and may not infact be real as they were just rumours floating around the set, but I hope you find it as interesting as I did.
Source: Anon