On the Disney website the menus are described as "Sample Menus" and places such as allears and this site are dependent on members submitting menus so I'm not sure you will be able to find the truly up to date menus at any given time.
We asked for the menus as souvenirs at the sig restaurants we dined at last month. One or two were printed daily so I don't know if those change more frequently. Comparing our menus with those on line the biggest differences seem to be in the fish dishes and the veggies/fruits that accompany the various offerings. Those seem to be more seasonal. The meat and poultry preparations didn't change as much, although the sides might be different.
Once you're at DW you can stop by the restaurants. Some like Narcoossee's, Le Cellier and Jiko had the menu posted outside. At any of them you could ask the host/hostess to see the menu.
