Happened to us at Disneyland on a really really busy day around thanksgiving.. they added hours That day AND added a showing of fireworks and fantasmic. It was awesome.
11/28 changed as recently as 3 days ago (MK and AK open an hour earlier) so you never know.
They also extended both opening and closing times for 11/25-11/27 10 days ago.
If you subscribe to touring plans and put your dates in there, it'll alert you when times (or expected crowd levels) change for your dates.