Variety's Anne Thompson spoke to Thomas Tull, the head of Legendary Pictures (co-financier with WB of Batman Begins
, Superman Returns
, The Dark Knight
, and others) a couple of weeks ago. I just saw it flagged up on Comics2Film. Here's the relevant bit in relation to another Superman film:
He's also vested in making the next Superman installment, which is still years away, come to life. While Bryan Singer has been working on Valkyrie, Tull and the folks at Warners have been listening to various screenwriters pitch their solutions to how to make the next Superman work. "It's an iconic character," says Tull. "After everything that went into the first film, it's important to make sure that nothing is rushed and we come out with a fantastic second film." One thing they all agree on: Superman needs a powerful antagonist, a "worthy opponent," he says.
So it sounds like they're envisaging a sequel, but since they're still only at the stage of taking pitches from screenwriters they're not far along in development (which makes a summer 2010 release look dubious given the size and complexity of a Superman film). The more time slips by the more likely it becomes that WB and Legendary decide to start from scratch with Superman rather than make a sequel to SR