you can kind of calculate how much and how quickly they will expand by seeing how much brood you have. that's just for future reference.
did you find any queen cells?
if you did, you can take the old queen, some frames of brood and food, and make a new hive. leave the queen cells behind.
if you didn't, you can just divide the frames of eggs, larvae, and brood between the old hive and the new. make sure the new hive has plenty of eggs and plenty of food. they can then raise their own queen. if you don't see the queen, don't worry. as long as the one that doesn't have her, has the resources, they can raise a new queen.
with a hive that full, i would immediately add a second box to the original hive...or the hive that has the queen if you move her. the hive that will make a queen needs to be watched. they may fill frames with food and not leave room for the new queen to lay. you will have to be ready to add a box to that one also.