I did it last Monday and thought it was an incredible experience. You will love it. It was my first time seeing WOC and I think I'm spoiled now - I can't imagine watching it any other way.
it's not just the dessert party. my 60 day window opened today for when we wanted to book our World of Color dinner package and those also can't be booked past July 2nd.
Last year when I was going in October, I started booking things in August, but there were still some things I couldn't book due to unknown scheduling. It took a couple weeks (which felt like FOREVER) before they opened up the dates I needed. I'm sure it's something like that going on, due to July 4th celebrations, etc.