Typically it's around August-early October.
I will say this much though, coming from someone that used to work at Walt Disney Travel... there is absolutely NO reason to book out this early, even if 2010 rates were available right now.
Be patient and even when 2010 regular rates come out, hold out for special promotional rates. Sometimes, depending on who you book with, you might not be able to make changes without a fee so just be patient.