It's literally dead after it stops making money when the devs turn the servers offline. If you release a FOSS battle royale, you understand that the game either needs bots or organizers to get enough players to fill it. That's no different than running Xonotic, just at a different scale. (There were/are also battle royales that operate with smaller player counts than PUBG or Fortnite or whatnot, which makes this easier to solve.)