The Last of Us Part II Factions isn't part of the game that released in late June, as Naughty Dog first confirmed about a year ago. Shortly after that confirmation, the developer addressed the topic in greater detail and revealed exactly why.

　　We wanted to address multiplayer in The Last of Us Part II. As we’ve stated, the single-player campaign is far and away the most ambitious project Naughty Dog has ever undertaken. Likewise, as development began on the evolution of our Factions mode from The Last of Us Part I, the vision of the team grew beyond an additional mode that could be included with our enormous single-player campaign. Wanting to support both visions, we made the difficult choice that The Last of Us Part II would not include an online mode.

　　However, you will eventually experience the fruits of our team’s online ambition, but not as part of The Last of Us Part II. When and where it will be realized is still to be determined. But rest assured, we are as big a fan of Factions as the rest of our community and are excited to share more when it’s ready.

　　If anything, though, the message got fans excited about the prospects of a vastly deeper The Last of Us Part II Factions mode.

　　Now that the single player game has been out for a few months, fans were expecting to learn something about it during this past 'Outbreak Day' (which was celebrated on Saturday, September 26th) but Naughty Dog did not oblige on the matter. However, Game Director and Writer Neil Druckmann did tease in a tweet it'll all be eventually worth the wait.

　　Thank you to all the wonderful fans for an incredible #TheLastofUsDay ! Your positivity and love is incredibly inspiring. Oh... and about that other thing... be patient. It’ll be worth it. ❤️

　　— Dr. Uckmann (@Neil_Druckmann) September 27, 2020

　　While we don't have any official ETA, it is reasonable that Naughty Dog will release The Last of Us Part II Factions alongside a PlayStation 5 enhancement patch to reignite interest in the game; we already know there won't be any single player DLCs, anyway.