I won't get into details, but I'm a journalist who handled the travel beat at one time for a mid-sized metro daily paper. A couple of years back, I did a Business Page report on WDW operations. These folks are abolute MASTERS at matching hours to projected attendance. What was completely obvious to me (both as a reporter and long-time visitors) after I did that particular srtory, was that a lot of the "back & forth" about the best and worst times to go ( Easter, July and XMas week notwithstanding) is a bit of a wasted exercise. They know how to move people. They know (believe me) within 500 to 1500 how many people to expect at each park on a given day as much as 15 days in advance. The computer models they use to do these projections are not only fascinating, but based on 25-plus years of historical data. They take everything from airline and hotel booking, long-term weather forcast, economic condition and geo-political conditions into account.
The result of all this blabbering I just did? You can see (quite precisely) by watching the posted hours of operation how the crowds will be. If they're staying open until midnight, it WILL be CROWDED.