There was never any doubt that The Last of Us: Part 2 is a story where Ellie is the star, but we now know that she's also going to be the only playable character.
The Last of Us: Part 2 demo shown at Sony's E3 2018 showcase was incredibly violent, but also very sweet. It showed a combat encounter Ellie had with the Seraphites, a cult whose members make up some of the enemies in the game.
In an extended version of that demo shown behind closed doors at E3, Naughty Dog was asked by IGN whether we'll be seeing more playable characters than just Ellie.
Initially, the answer was a very typical "We aren’t saying anything about that yet," which co-lead game designer Richard Cambier provided. A moment later, creative director Neil Druckmann decided to confirm that, yes, Ellie is the only playable character in the game.
The original Last of Us let you control Joel for a the majority of the game, but Ellie was a playable character in late parts of the game. Considering how old Joel would be in the sequel's timeline, it's probably best if he didn't see too much action.
Of course, as the site points out, things may still end up playing out differently in the launch game. Naughty Dog could simply be saving a surprise for players to discover during the course of play.
The Last of Us: Part 2 does not yet have a release date.