According to NBC president Angela Bromstad, while it's unlikely that we'll see more Chuck before 2010's mid-season launch of season three, it's not impossible that season three may be longer - and later - than originally thought.
Talking at the NBC panel at this year's Television Critics Association Press Tour, Bromstad - NBC's president of prime time entertainment - answered two rumors surrounding Chuck's third season. Saying that the show is "on a great track creatively," she went on to say that there are currently no plans to move the season earlier on the calendar (It's scheduled to start airing in 2010, following the conclusion of Heroes' fourth season), but that there may be more than just the announced 13 episodes. Bromstad said that it's possible that the season may
run over into the summer… Those are discussions we will continue to have.
Also during the appearance, Bromstad said that we shouldn't be too worried by Bryan Fuller's second departure from Heroes:
It doesn't mean anything [for the show] one way or the other... Bryan came back to be in the writers' room initially and helped [them] get back on track.
But, wait. Don't we need someone to stick around and make sure it doesn't go back off track again...?
Press Tour Diary: NBC bosses tout plans for 'Chuck,' 'FNL,' 'Southland,' Paula Abdul, and more! [Entertainment Weekly] and NBC already getting cold feet about Day One? [SciFi Wire]