Well yes and no.
I am inclined to think WDW has enough customers that a WDW late night delivery service offering pizza, warm cookies, and a few other munchies would do quite well.
MK used to regularly stay open until midnight and later. I am inclined to think people are willing to stay out late...except that G+ has somewhat crippled the appeal of staying late.
Under G+, there is a strong incentive to be awake at 7am. If I'm awake at 7am, then I might as well get to the park by 9am. That wasn't the case in the past. So while Disney is partly saving money, they are also hurting their business by not offering late night options. (parks and food)
This is part of what I dislike about the G+ era. It somewhat forces me to be a morning person, and to tour the parks with all the morning people.