11/16 - Executive producers Damon Lindelof and Carlton Cuse reveal: It's always possible [Shannon] could pop up in someone's backstory. But she is definitely dead. When a character dies on the island, they stay dead. In the same moment that we decided Shannon would die, [we also decided that] Ana-Lucia would be responsible for that death. It would be the first time one castaway was responsible for killing another, and it would give so much inherent conflict and trauma [heading to] the merge. We're walking a very tenuous tightrope with her, but we feel that over the course of the next two episodes the audience will hopefully get a better understanding for that character and what she's been through. [Shannon] was shot. Walt's disappearance and, ultimately, Michael's efforts to reunite with him were part of a grander plan. As we move into the middle run of episodes, we're definitely emphasizing the Jack-Kate-Sawyer romantic triangle. The level of sexual tension between those three characters is definitely being ramped up. As the respective leaders of their respective units, Ana-Lucia and Jack have a great deal in common with each other, and that's definitely something we're going to be exploring. But [the fact that] Ana-Lucia inadvertently murdered one of the members of the tribe doesn't exactly [lend itself] to candlelight dinners and walks on the beach. She is a woman; she will have romantic entanglements. But I think the one that will begin to emerge over the season will be the one that you least expect. Source: Ask Ausiello @ TV Guide
-the following are general season spoilers-
We're definitely going to be paying attention to [the Charlie and Claire] relationship, but it's not going to turn in ways the audience expects. I think that [the] question [as to what the numbers mean] will never, ever be answered. I couldn't possibly imagine [how we would answer that question]. We will see more ramifications of the numbers and more usage of the numbers, but it boggles my mind when people ask me, "What do the numbers mean?" You'll learn more about [why Ethan abducted Claire] this season. [We still plan on revealing why the plane crashed this season.] In the next string of episodes, one of the really compelling backstory elements is what happened to Jack's marriage. We think Julie Bowen is amazing and she and Matthew Fox are so great in scenes together, and I think the audience is really curious as to what went wrong there. And you should pay attention to Mr. Eko's stick. That stick is an important ongoing clue. [We will learn more about the monster this season.] Source: Ask Ausiello @ TV Guide
my comment: the producers seem to make it very clear that ana is responsible.