Most likely the flights are not "booked" but group space is blocked. That will probably mean more availability will come closer to departure once they realize any blocked space is not needed.
Agreed, in terms of both hotel and flight space, the convention organizers most likely have it all locked up for now. Some may become free later in the year, but it's also possible that some flights will actually need every one of those seats.
I wonder if leaving town for that week might yield better results.
