Some will change, but for the most part they will be the same or similar. Like, for example, Coral Reef may change the exact types of fish on the menu based on what is available, but will still be mostly seafood. CS is similar too. Cosmic Rays will probably always be typical fast food, chicken and burgers, while Sunshine Seasons tends to have slightly more interesting fare. Some places also change on purpose with the seasons, like Minnies Seasonal Dine in HS. That one will probably to tricky if you want to eat there because the types of food on the buffet tend to be fairly similar, the actual menu changes with the seasons and tends to be geared toward the nearest holiday. Christmas is cranberries and turkey, summer is more salads and lighter dishes. Of course, there are always kid friendly foods at the buffets too, and then the desserts are decorated for the seasons.
If you tell us what you're looking at, we might be able to give you an idea which places have switched menus recently and probably wont again this year, or which ones tend to change frequently.