There is a section on the Swan and Dolphin FAQ at the bottom, that gives tips on how to improve your chances of getting an upgrade. Even when the hotel says it is to capacity, I have heard that there are always extra rooms. I would follow the directions contained in the FAQ, and make sure what you want is put on your reservation.
ex. Balcony room , high floor facing Epcot...that would give them more to work with than a particular room. Good luck!