Is it your only colony?
If so I would let it get stuffed, not to a swarming stage. Just give plenty room and let it build up.
Then split and move the Queen with the split. With about one or two frames of sealed&growing brood
with all the bees on. Shake a few xtra bees in. Make sure to leave a frame with eggs/day old brood in the mother colony, leaving it in the old place. they should rear a new Queen.
I don't like waiting till they are ready to swarm to do this.
I split one last year that had several capped queen cells and they still swarmed, twice. Although I did get a good colony from it. The split did not swarm and also produced a good healthy colony.
I ended up with 7 colonies last year and haven't lost but one this year so far.
Still Recouping from my lost from year before last.
hope this helps. :)doak