December/January are extremely slow months in the rental market. I don’t think this unit would be easy to prep and fill in time for a Jan 1 move-in.
You can ask to get out of your lease, but if the landlord does not fill the unit, you are liable for that month.

Subleasing for one month does not seem worth the hassle. But, if you are anywhere near the beach or attractions, you couyld consider renting it out to an out-of-town family member or friend for a week or two around the holidays.

If you close in December your first mortgage payment will be due on Feb 1, so you shouldn’t have any real cash flow problems (but I do understand the desire to save a month’s rent).

Consider yourself lucky that you don’t have to move to an interim place between your current rental and your new home. We’ve had to do that in the past and would gladly have forked over an extra month’s rent to avoid the hassle and extra costs of doing it that way.