The decision to remove The Last of Us Part 2 won't have multiplayer, despite its popularity in the first game.
Multiplayer in The Last of Us Remastered, on PS Plus in October.
After Naughty Dog confirmed Factions wouldn't be returning for The Last of Us Part 2, the news gathered a considerable amount of media and fan attention. In response, reportedly comes on two discs).
Naughty Dog's statement seems to imply that, while the team's focus has been on single-player, at least some form of multiplayer development could be taking place alongside it. It could end up being a sort of standalone expansion along the lines of Rockstar's multiplayer titles, like Red Dead Online. The Last of Us Part 2 took quite a long time to develop, so it could be a while before Naughty Dog is ready to show its multiplayer mode - although, if it's anything like the original game's multiplayer, the single-player mode's mechanics have likely already provided a basis for Factions.
Naughty Dog released a return in the Last of Us Part 2), which will be useful when she has to avoid the new scent-tracking dog enemies. It could be interesting to see how these new mechanics would play into a The Last of Us Part 2 multiplayer mode, and it sounds like Naughty Dog is planning to deliver that, eventually.
Source: Naughty Dog/Twitter