Yes it does thin out but in my experience the relief is not immediate. NOS will still be pretty busy w the second showing of F!, and Adventureland and Frontierland can have CMs restricting traffic flow. Fantasyland stays closed for awhile as the fire marshals inspect it to ensure that no embers have landed there. Toontown is closed and stays closed. So that means right after fireworks there is really only Tomorrowland and so that can be crowded as a result. But hang in there, once about 45 mins have passed it gets better and then better and better as you get closer to closing. And, as you may know, you can jump in line for any ride (even if it says 60 min wait) at 5 minutes before closing as CMS let all people in line ride no matter how long it takes.