The long and short answer is "it depends." The seem to try to arrange the busses by resort areas--like Epcot area resorts on one bus, Downtown Disney area on another, etc. Of course, this is dependent upon the DCL reps organizing things well and the numbers of people arriving in any given time frame. They like the bus to be reasonably full, but at the same time, they try not to keep you waiting too long for a bus or to have the bus hit too many resorts.
It would be unlikely that your bus would go only to one resort (unless you were very lucky.) However, it should only go to a few, and they should be close together.
All that said, our last DCL bus went to 7 resorts. The driver complained to the DCL rep as we were boarding--she told us to get on that bus, and the driver told her that he now had 7. SHe told him that it was her mistake, and to "just do it this time." Fortunately, we weren't at the last resort!