Sign on right at the 8 AM eastern time window. If there is nothing there, then WAITLIST it, AND keep looking and refreshing it every few minutes. If nothing shows up, keep checking back every half hour or hour during the day.
People who are booked into those rooms will also be changing to other resorts, just like you. And this will free up their rooms, for you to book, depending on how many people are moving. These rooms will then show up in inventory a few minutes later, with a NEW SEARCH. But, you need to check back regularly, since other people will also be looking to change at 7 months, and pick those up.
The changes are most likely to happen within the first few hours after the opening of the window, but if it doesn't happen, don't give up. Waitlisting it does give you possibilities, AND, they don't need to necessarily drop their old reservation and change exactly at the 7 month window. You would think that is when they are MOST LIKELY to change, but, like you, maybe other things will open up for them later, and they will drop it later, even days later, and you can pick it up.
If you go into your current reservation through the MODIFY button, then you can Waitlist it, and the system will automatically fill the waitlist request, and use it to replace your current reservation, if you want.