There is almost always some type of discount going on at the Walt Disney World Resort. The exceptions are typically for check-in on or around major holidays, which are also extremely busy times at the resort. If you book with a travel agent, that agent should monitor for promotions to help save you money and automatically apply any that would come out to your existing reservation.
In general, very few discounts are offered in August. If they are, it will be later in the month.