Yes, WoW maintenance has been extended. This happens, often.
That’s just sort of how technology works. It’s unpredictable, and often finicky. Would you rather they go live with errors that make it unplayable, or fix it before making it live so we can play properly?
It’s impossible to know whether or not a patch is going to decide to bug out, and no amount of prior experience patching will help predict that.
Chill out. Watch some Netflix. Read a book. Go for a walk. Goof around on another game. Just trust Blizzard to get it up when it’s ready to play.