In case you haven't checked in on Attack On Titan 2 lately, Koei Tecmo has been working to keep the game supported beyond the initial release so it doesn't fall off the grid like the first game did about three months after release. As part of that, the devs have added a brand new update that is free for everyone to download called Expulsion Mode. The new mode goes a little hand-in-hand with the third season on the way but doesn't directly reference what's to come in any form. As you might have suspected considering the word "free" in the description, this is a battle royale game with six players trying to destroy as many titans as possible in a certain time limit. Here's the trailer for it to give you an idea.
In order to play Expulsion Mode, you'll need to go to the menu and select Another Mode, then make your way to the white tent on the right to gain access the newly added Multiplayer Mode. It will be identified by an NPC with a globe icon. You'll also notice two more modes have been added in the form of Annihilation Mode (4-on-4 competitive) and Predator Mode (where you play as the titan instead of the fighters).