Well I don't know about officially scheduled events yet but they generally do stay open at least until 12 on July 4th. In the past Epcot has done two rounds of Illuminations(one at 9 and one closer to midnight then the BIG fireworks at midnight-or is it 11?) MK also does a similar two fireworks shows that day. MK has filled to capacity the last three times we have been there on July 4th(although if you are a resort guest it does not matter) If you are a pin collector they always have special limited edition July 4th pins in each park-these usually sell out as well by lunch time. We are planning on watching the fireworks from our hotel this year as we have a very little one. If the past is any indication the parks that get the most crowded on July 4th are MK and EPcot(although in Epcot you don't notice as much because it is so spread out.) I am wondering if this year will be even worse because I think July 4th is on a Monday. We'll see you there!
I have never used the more crowded on this day thing and have never really had a problem. Although they say most people hit MK early in their trip(as in Monday) so avoid it on that day. And I think AK is more crowded on weekends. But we just go with the flow. Yes it is crowded that time of year but with the parks open so long it never has been a problem.