Disney published the August 2015 Disney World operating schedule at the usual link: http://media.disneywebcontent.com/StaticFiles/ParkHours/WDWTravelAgent_august.pdf. Click “refresh” on your browser to load the newest version. It doesn’t look like there are any surprises this year as far as Extra Magic Hours/nighttime entertainment/early closures throughout the month.
The later you go in August, the better as far as crowds are concerned. Labor Day is late in 2015 (September 7th), but that shouldn’t have a significant impact on how crowds are dispersed between the last week in August and first week in September. If you’re flexible with your dates, September 8th to 15th should see the lowest attendance of the year. Otherwise, if you can swing the last week in August, you’d be better off than one of the first three.