Some outfitters will move you, others won't.
Some of them are constantly flying clients in and out and may have people that will be watching the migration, so they know where they are at any given time. That said, Caribou can move great distances in short periods of time so they could be in one area one day and completely gone the next.
Best to ask your outfitter what their policy is with regards to checking in with you and moving you if you aren't seeing anything. I personally wouldn't and haven't hired an outfitter who wouldn't move me if needed.
I also asked for references and called or emailed as many as I thought was needed to get a good idea about the quality and professionalism of the outfitter. I not only asked about their experience with the outfitter, but the quality of the animals and the numbers they saw, and asked if they had been moved, how frequently the outfitter made contact, if they were able to fly in/out the day they had planned and if not, why.
You should also ask the outfitter what kind of aircraft they are using and how much they allow a person to take. Also, ask what their hunting area is like (terrain, water source etc.) and how many other outfitters are putting people in the same area.
It's also helpful to know if they are providing fully outfitted camps or if all equipment etc. is on you to provide.