I worked for target in the toy department about 4 - 5 years ago now and this is true and display items would just be crushed in the cardboard compactor out the back. They never asked for any displays back, We had a cool Playmobile display diorama in a plastic display case that when it was over we put in the bin out the back.
But a lot of the time the posters and displays would just go to the staff there, a mate of mine has all the display items from the first movie, posters cut out etc.