I was talking recently with a friend in Main Street Ops (not necessarily someone who would be super privy to "upper level" decisions like fireworks and entertainment but still someone who has a good sense of what's going on at MK at least), and he mentioned he couldn't see them extending hours until they brought back more entertainment offerings, specifically fireworks. Apparently, they're just not seeing the evening Guest retention that they normally do, which is why MK's "extended" hours only are to 7pm for the time being. Even as weekends have picked recently, apparently they're just not seeing the Guest spending levels that would warrant really bumping out hours. While dessert parties and corporate events certainly help cover the cost of the fireworks, the real reason Disney has always done them is to keep Guests spending money (shopping, snacking, having dinner, etc...) until the end of the day. Without that carrot, it seems that you have a "slow, trickle" of Guests leaving "throughout the late afternoon" (his words) rather than a large rush at night. With that in mind, I'd have to imagine you'll see more shows, entertainment offerings, and eventually fireworks until we see decidedly later closings. Gotta give Guests a reason to stay. At least at MK.