If you see drone cells in the final stages of development, go ahead and make the splits. It will be another 15 to 18 days until the new queens take their first mating flights.
If you do splits, just make sure they have enough bees to cover the brood and overcompensate for drift if your splitting and keeping them in the same yard. I split about 70-30. Meaning I move the old hive, the old queen, and 70% of the bees on the frames to the new location in the same yard. This will allow a portion of the bees to fly back to the old location where 30% remains and boost their population with the new queen.