The 2011 itineraries were released near the end of July 2010. In previous years they have been released first or second week of August. For the last two years
ABD has offered no incentive for booking early. Instead they have released offers 2 to 3 months after releasing the new itineraries. In 2009 (for the 2010 trips) an offer came out in Oct for a free 3 day
DCL cruise and then later (in March as I recall) they sent out Pins with discounts. For the 2011 trips a Visa gift card offer came out in Nov 2010. So there's not really any reason to book as soon as the trips are announced. Some trips do fill up, but I've never seen any indication that they fill up quickly.