Set a fare alert on Google Flights or Skyscanner or both. There is a reasonable chance the price will drop between now and December. Consider setting a price alert for Premium Economy as well, you may find that it drops to close to what you are paying for MCE. I am guessing that right now the difference between coach and PE is something like $1000. Don’t be surprised if that drops to $300, at least for a short period of time, if there are still available seats in PE.