Every year, when I go into Universal Studios Florida just before it closes at 5 p.m. to enter one of the waiting pens for Halloween Horror Nights, I hear people complaining about the early closing time. The park has to close early to clear out all the day guests before the hard ticket event, and it makes some of the day guests unhappy.
This year, early birds won't have as much cause to complain, as the park will open at 8 a.m., giving them an extra hour to enjoy Universal Studios Florida in the morning. Islands of Adventure next door won't have an early opening, but it stays open after its sister park closes.
Of course, if you're attending Halloween Horror Nights, I strongly recommend getting a day ticket so you can stay in the park after all the day guests are sent out at 5 p.m. You can wait in one of two holding areas, and you get a jump on the haunted house lines when you're released. It takes a while for the hordes waiting out front to filter into the park, so you can easily do two or three houses with no line while they're making their way in.
Expect the lines to be particularly long this year with so many popular intellectual properties like Cabin in the Woods, Evil Dead, The Walking Dead, and An American Werewolf in London. To hear more about the IP houses, start with this article. You can do a walk-through of one of the houses (The Walking Dead) in this article.