AP holders have always been allowed to purchase the dining plan, but in the past they had to purchase at least a one-day base ticket in order to get it. Because the ticket could be used toward the cost of renewing the AP it wasn't that big a deal to do it.
You'd probably have to wait until they release AP discounts to see if they would apply to an AP room/tickets package in September. Or, you could book an AP room/dining package and then change it to the discounted room when they're released, if you know you're going anyway.