The event will be held at Apple's Cupertino headquarters instead of its usual Yerba Buena Center fête; that's not entirely out of the blue, though, as Apple last played a home game for the similarly iterative iPhone 4S. You can expect preorders to come soon after, with shipments arriving on Sept 20th.
Otherwise, the details of what we're expecting haven't changed much since AllThingsD first reported that Sept 10th would be the day of the big reveal. The only thing that's certain? There won't be many surprises. More here.