I'd say close to 100% if you book at 7 months out and can take an Inn Room. July is not as busy as some other times of the year and other than the Beach Houses and Xmas to Easter, VB is pretty easy. July will be the next busiest time (esp the 2 weeks that the 4th tends to fall on) but there is a huge difference in demand compared to Xmas, Presidents week, March and April especially.
Just to add slightly to Doc's information. IF you book through MS for all your nights (cash and/or points) AND it's the same exact unit type, you will not have to move. If you end up with different unit types such as a lockoff vs a dedicated 2 BR, there's a great chance you'd have to move. If you had a 1 BR or studio part of the time and then a 2 BR lockoff for a portion, you might or might not have to move. However, you still would have to do a second check in in many of these situations. I've trucked up to the front desk at 6 am several times to get new keys and do a second checkin. Though in all the times I have had to do this it was for different unit sizes even though we were able to stay in the same unit we were in, just open or close the lockoff.
And if you book part through CRO and plan ahead, there's still a good chance you'd not have to move but I'm pretty certain you have to do a second check in for this situation.