I don't want The Last of Us to become a franchise that starts over with a completely different story and characters in every installment, because I don't want this to become another Call Of Duty, [Assassin's Creed](tag:437814), or Dead Rising.
I think this absolutely should be a franchise that charts the lives of Ellie and Joel, or at least one that charts the life of Ellie. We don't usually see a zombie style game like this that's so focused on it's characters. You know why a game like Assassin's Creed or Dead Rising changes it's protagonist in each installment? Because the developers don't care about the characters, they don't care about the story. Ubisoft and Capcom (the companies behind Dead Rising and Assassin's Creed) are companies that don't care. They do not care what story they tell, or what happens to the characters in those stories, that's why a company like Ubisoft never keeps its protagonist.
But Naughty Dog has shown that they do care about the characters they create, that's why every Uncharted game chronicles the life of Nathan Drake, because they have so much passion for that character. If Uncharted was made by a company like Ubisoft, they probably would have made each game with a new protagonist, they would have also made one each year as opposed to every other year.
Going back to The Last Of Us, I believe that Ellie is a character who is more than capable of carrying a franchise, and I would both hope and expect that Naughty Dog shows the same passion and love, for her, that they do with Nathan Drake. Like I have said, you don't always see this type of game be so focused on the characters and what they go through, rather than the gameplay or the world. If The Last Of Us become episodic, it would take away from that aspect of it, you could say that it would be just as focused on the new characters, but really it wouldn't, because changing the main characters at all would show that Naughty Dog cares more about the world and gameplay than the story, because they would be abandoning the story and characters they claimed the game was really about, to focus on the aspects of the game they claimed to be just a side story.
The Last Of Us is not an exploration of culture, or what places would be cool to see get destroyed by the infected, it's a character study. The Last Of Us is about these two characters and what they go through, and who they are. That's why the ending is so debatable (and why making Joel the bad guy is such a terrible idea), because it's not about right or wrong, it's about what lengths a man would go to, to protect those he cares about, and not just what any man would do, but what Joel would do, that's why the ending is not player choice, because the game is not about the player, or the rest of humanity, it's about the bond between two people, and not just any two people, it's the bond between Joel and Ellie.
The sequel should focus on Ellie, it should show us what type of a person she grows up to be, as a result of the events of the first game, that to me is a story far more worth telling, in respects to this franchise, than some other random group of survivors.