I read some months back here on The DIS that someone was told their family had to get out of a restaurant (forget which park and which restaurant) in half an hour if they wanted transportaion back to their resort.
I dare say cautiously that the restaurant was bluffing and you should enjoy your meal and not take the restaurant up on that suggestion.
It is possible that buses that far after park closing may sit for awhile to gather guests and make stops at numerous resorts.