Skywest, operating as Delta Connection, has won the bid for Rhinelander and will take over flying there in the next handful of months. I'd say it's even money on if that change will be before or be after Thanksgiving. They have not announced it yet, but the DoT has made the award.

If you book the Frontier trip now and Delta ends up taking over, Frontier is required to work with the new carrier (Delta/Skywest) to rebook you. My only concern is tht I'm not 100% sure that you will be rebooked without any additional fee. I believe that's how it is supposed to be, but I am not absolutely certain.

So if you do book into Rhinelander, you're probably okay because either Frontier will still be flying it, or if Delta takes over by then they are required to rebook you. But again, I'm only about 85% sure that you would be rebooked wtihout any difference in fare due.

Have you checked Iron Mountain or Escanaba? I see Wausau for abot $420 round trip on those days on American and United.

One other option -- you could fly Allegiant into Appleton, nonstop from Phoenix/Mesa Airport (that's not Sky Harbor but the other one). It is not a daily service so you'd need to adjust dates a little, but it might be worth the nonstop flight and cost savings:

Flights from Phoenix/Mesa to Appleton in mid November
15th $80.80
18th $140.80

Flights from Appleton to Phoenix/Mesa in late November
21st $120.80
25th $186.80

So these dates have round trips anywhere between $201.60 and $327.60. Be aware with these guys, however, that there are fees for everything including $10 for booking online, around $15-30 for a carryon bag, and even $4 for using a credit card instead of a debit card when you pay. So just be aware your fare could creep up some.