Personally I would not wait for August incentives if you are looking to buy. I bought in June and it saved me $2000 over July. Demand is up and supply is down. Warren truck was shut down for two weeks in July while dealerships were still open, so inventory is logically depleted too.
This article notes that "transaction prices" are also up.
Even if rebates hold, it does not seem dealers are having a hard time finding buyers so they won't have to deal quite as much.
Just my guess....