Most of the full service (but not all) add a special holiday selection to their existing menus. Some will be more of a gourmet approach (pumpkin soup, etc.) where others will be the "traditional" (whatever that really means) fare.
If you have a favorite full service restaurant you can expect a special selection.
You can also call WDW Dining and ask them what is being served for the holidays at a given restaurant. However, they may not yet have the Christmas menus.