If you pre-ordered or purchased the season pass, anyway. Everybody else waits until 20 December, because, uh, you didn’t pre-order or purchase the season pass. You’re like the second deployment after the recon team, which also means you’re probably more likely to survive because the other guys tripped all the mines, but maybe I’m taking this metaphor too far.
Next to the new map, the update also adds a spectator mode, a new custom game mode, and the obligatory list of adjustments and fixes to in-game play mechanics, vehicles, weapons, and more.
The full patch notes can be read over here, but there’s also a a series of videos by toober Westie that show off the important stuff if you prefer your info dumps with more colours and pictures.