... as stated in this press release. The other information in the previous post on this subject still holds good.
As I understand, there's no fallback period for launch after September-October: by the time Dawn would arrive in the asteroid belt following a late launch, Vesta and Ceres would be too far apart for the spacecraft to visit both of them. [I don't have an authoritative reference for that statement, but I may add one if I get time to look around online in the next week or so.] One hopes that they've cleared their slate in September, and that the weather holds.