I don't know about that particular week (late Sept), but we just booked OKW GV for the last week of this August a couple of weeks ago (well under 7 months)!. You never know!
"point switch" with an OKW owner? (Just an idea No idea how you could work that...I think I would just rent the points from an OKW owner) Or book a GV at SSR at 11mos, and that way if you can't get it at OKW at 7mos out, you've at least got the accomodations you need..?
You've probably thought of all that anyway LOL! Have fun planning!!
That's not a very busy time, and I think there is always a possibility. You wont know until you try, and if it doesn't work out, you can always do a 2 bedroom plus a studio.