I don't know when it will open but it's best to wait anyways. That is a slow time of year so no need to book very early out. The main reason to wait is because they often offer heavy discounts for that period. Those deals may not be listed until November or so.
I've always booked online through disneyworld.com. Check other websites such as mousesavers.com for any deals currently listed as codes may need to be entered into the site or given over the phone. Last Febuary a 7 day stay for 2 in a Value resort with MYW passes and DDP saved us $400 and included free park hopper and water parks and more options. That deal had to be booked by mid Dec. I am not sure when the discount was first listed but I believe Nov.
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