https://www.gamespot.com/articles/halo-has-no-plans-for-battle-royale-mode/1100-6460565/

Halo developer 343 Industries has no plans to introduce a battle royale mode in Halo 5 or Halo Infinite, it seems. Halo franchise manager Frank O'Connor said on Twitter that the studio is not currently working on a battle royale mode at all. That said, O'Connor pointed out that Halo 5's Forge tools are absolutely robust enough to make a battle royale-style mode, though it wouldn't be possible for it to contain 100 players like in PUBG or Fortnite.

"We are not currently working on a Battle Royale mode," O'Conner said. "If you really want it, make a version in Customs with Elimination as a basis. Obviously it'll be compromised in terms of size, but you can make something similar now."