For the last two years, the package prices have come out mid-August. I made our June, 2007 reservations in August, 2006 and our June, 2008 reservations in August, 2007.
You can book a room only reservation but it will be at 2008 rates and they will change when the 2009 rates come out. When the package prices come out, you can cancel the room only reservation and book a package reservation.
If you have your heart set on a certain resort, you would be better off booking the room only. At least that way, you know you will be staying at your choice of resorts.