Rooms for September are now available. If you have points, make sure to redeem them. Just a heads up though, you can
only hold 1 room at a time it appears. I tried to get another for a different day and it won't let me. So if you are wanting to go between now and then, it'll won't let you book another room until September. So if you are planning a trip between then and now, you may want to wait.
Also, some bad news, looks like Saturday is unavailable. I booked Mandalay Bay for Friday night though. Here is the calendar for September.