This is something so simple in concept, I can't believe it has taken this long for Disney to do.
I know cooking for gazillion guests every day is not an easy thing. You find that food supply makes it tough to offer certain foods all the time. That's why a little variety in a weekly special dish makes so much sense.
Having a weekly special is a good way to let the kitchen experiment with new dishes. It gives the guests a little variety which is nice.
Where I think the disney dining plans popularity had killed off a lot of creativity from the kitchens, I think the trend has reversed. Dining plans seem to decreasing in popularity, and in turn that is allowing the restaurants to start to bloom again with more creative offerings.