Kim, I can't forecast next July availability but I have found its very hard to get a DVC unit at VGC. We apparently were lucky last year to get a 2BR unit after our trip. I don't recall exactly how early I booked that but obviously it couldn't have been any sooner than 7 months before.
You can also use DVC points to stay in a regular room at the Grand (or the other two hotels for that matter) and sometimes the "exchange rate" is ok as compared to the regular hotel rate. Val & I have done that a couple of times, but for our next trip we're finding the cost of the DLH would be cheaper with an AP discount than using points (at least in September).
So, not really an answer to your question other than to be on the phone at the 7 month window.