You can make a room only booking for up to 499 days in advance, so I think you could do it now. They will give you a rack rate with this year's prices, then I think they will adjust the price when the 2013 rates come out. You would have to pay one night at time of booking and the remainder at check in.
You would be able to re-book to change this to a package if a better deal comes out, or change dates, or apply a room only discount at a later date if any of these come out.