I believe that OKW has 27 Grand Villas. My understanding is that they are fairly difficult to book any time of the year at the 7 month window, but OKW owners can probably give you a better feel for that.
As Granny stated, there are 27 GVs and they are typically in high demand. Late August (especially the last week) tends to be a slower time at WDW in general and you may find success securing a reservation at that time.
You might also consider trying to find an OKW member willing to make a reservation for you before 7 months.
The real answer is that you'll never know until you call MS to make the reservation. Reservations open up all the time, so even if it's not available when you foirst call, the waitlist may still offer success.