Of course Fallout 76 is getting a battle royale mode. Nuclear Winter was the other free Fallout 76 DLC announced today and it'll put up to 52 players against each other to see who will become the Overseer of Vault 51.
Like other battle royale games, there's a circle around the playing field that gets smaller and smaller as time goes on and this circle is a circle of fire.
You can try out Nuclear Winter for free between June 10th through the 17th on all platforms.