The hours that have been posted are from the Travel Agents Calendar, which although not official, is generally pretty spot on with the real thing. The official hours should be released before the end of the month though.
The Sept hours are up on the WDW site, but hidden. Go to August 31st then change the end of the page link number to '20110901' which will bring up Sept 1st. You can then scroll through each day to see the opening and closing times. You'll need to do this for each park though.