The Plaza Restaurant in the Magic Kingdom will have more walk-up availability later this summer.
Beginning on July 17th, reservations will only be available between 11 AM and 12 PM. For the rest of the day, the restaurant will be open for walk-in guests.
The recently opened Jungle Cruise Skipper Canteen had recently been reserved for walk-up guests, but has since changed to allow advance reservations to be made. It appears that the Plaza will now be taking up the table service dining walk-up role.