Variety blogs talks about how "summit is pondering twilight finale.":
Sources said Summit has so far only gone as far as setting scribe Melissa Rosenberg--who wrote the first three films--to finish the series, but Summit has to clear several hurdles before telling Rosenberg if she should write one scripts or two.
Among those hurdles is figuring out whether “New Moon” director Chris Weitz will respond favorably to overtures from the film company and the cast to return and shoot two more films, back to back.