Coral Sea is allegedly designed to "showcase the intense battle in the skies, offering an all-new Air Superiority game mode." Battlefield will release "this summer" according to the latest press release. Last we were told it would release in June for $15, and the PC version is still scheduled for September. (There's no word on if PC players will have to complete a similar challenge to unlock Coral Sea, but we're looking into it.)
Update: An EA representative got back to us and said, "Yes, Coral Sea will release with the PC version."