Hi Carly and welcome to the forum! Yes, the bees will swarm every year in spring once the colony is large enough. It’s just how they reproduce. You can do a split to pre-empt a swarm, but the timing is important - as in your query:
If you’re in time to make a split, you definitely want to take your existing queen with it since she’s the one who would leave the hive with a portion of the workers as a swarm. As you’ll read, if she has been laying well, there will be young larvae for the workers to choose from in order to make a new queen.
Rather than describe the different timing scenarios and options, I found this thread for you - the Wally Shaw swarm prevention booklet in it might seem like a lot to get through, but is a must-read for comprehensive practical swarm guidance:
You can use it to figure out your game plan based on what you see in your next (ASAP) inspection. You don’t have to wait for your new Flow to arrive - you can probably pick up a deep brood box from a local supplier to use now, and then transfer into the Flow later. Or leave them in it, since it’s compatible with the rest of the kit.
Please keep your questions coming and you’ll get loads more help!