Too late for a split?

One of my hives that swarmed twice this year and then I split in two has supercedure cells in it. I cant believe it, there is what looks like a beautiful young queen mated and has been laying great since the middle of July but the hive has decided to supercede her. The hive was 3 boxes high and doing great, but during an inspection on Thursday I discovered 3 capped swarm cells and a queen cup with an egg in it. I finally decided on Saturday to make a split, at least to increase the chances that one will re-queen, I can always put them back together if one doesn't get mated. I also noticed that there are not many drones left in the hives so I am not quite sure how well mating is going to go. I read on Michael Bush's website that he does a split and leaves the hives side by side, and can swoop them around if one has more bees than the other. So its something new  and its worth giving it a go. Fingers crossed!