A number of multiplayer assets that have been found within the files of The Last of Us Part 2 suggest that Naughty Dog's standalone multiplayer title set in the same universe could be a battle royale. YouTuber Speclizer recently uploaded a video to their YouTube channel showing off some of the game's hidden assets which include a map as well as several textureless devices which hint at unique in-game abilities.
One of these devices is named "Listen Mode Device" which implies that players have to equip the item in order to use the "Listen Mode" used by Joel, Ellie, and Abby in both The Last of Us and The Last of Us Part 2. Considering "Listen Mode" is a built-in mechanic in the single-player games, it is almost certain that this asset came from some kind of multiplayer mode Naughty Dog was working on at the time.
Speclizer also claims to have found a compass as well as a player count in the hidden assets, both of which are commonly used across the battle royale genre, although these are not included in the video. This isn't concrete evidence that Naughty Dog's standalone multiplayer project is definitely going to be a battle royale, but a battle royale title with a Last of Us twist could set it apart from the more popular titles.
It's clear that these assets (if they are connected to a multiplayer mode for The Last of Us Part 2) were left as a result of Naughty Dog starting development on a multiplayer mode. Naughty Dog then started developing the mode as a standalone game after it became too large, addressed by the developer itself in a statement posted to Twitter back in September 2019.
News about Naughty Dog's mystery multiplayer game has been thin on the ground since then, but Naughty Dog has been hiring recently for said project, implying that it might still be a while before we hear any sort of announcement from either Sony or Naughty Dog.
Source: VGC