ABC is so secretive that it has censored the most part in the preview to the next episode of "Lost". But what can be derived from the glimpses are some things which are concluded on the previous episode. Someone bad is coming to the temple like Jacob had said and Claire sends a warning to the inhabitants.
The episode title, "Sundown", indicates the opposite of sunrise which means Japan. A few [SPOILERS] have been circulating around and they include Dogen explaining why he left Japan for the island. Also, there would be a scene of Ilana holding Ben at gunpoint. This explains Ilana's significance and answering why Ilana was included in the season 6 promo poster along with the show's more primary characters.
Despite the title and the temple story, "Sundown" is more Sayid-centric. According to the synopsis, he would be faced with a difficult decision. It has been reported a while back that Andrea Gabriel is back to reprise her role as Sayid's beloved Nadia on this particular episode. Shooting reports said that there will be a scene involving Nadia, Sayid and Jack in a hospital.