Not really sure if this will help you out or not but, I just wanted to share my bounceback offer...
We were at the World last year 9/25-10/2. The offer left for us was:
Free Dining with either of these vacation packages:
5 night/6 day package @ a Value Resort for $60 per person per day in a standard room
or
5 night/6 day package @ a Moderate Resort for $75 per person per day in a standard room
The travel time frame was 8/15/10 - 9/30/10
Book before the end of your trip and make a $200 deposit.
So, there will be a certain travel time frame for the bouncebacks. I can't say for sure that it's always for the same time the following year of your trip as some Disers have said they've had offers that were for the same year. Last year we did the free dining and paid rack rate for our room. The bounceback offer was free dining and 50% off our moderate room. When we go back this fall, it could be something completely different.
I know I probably didn't help but, I just wanted to describe what ours was to give you a better idea about them.