We're getting a new character in the upcoming single player DLC for The Last of Us. With no mention as to whether or not this DLC will be an epilogue or a side mission story with Joel and Ellie, the DLC might focus on a character that has never been seen before but is still tied into the plot of the game. I believe this might be the story of Ish. Little is known of Ish considering he was never seen in the game.. all we know about him is revealed by a series of notes found throughout The Suburbs chapter of the campaign.
When we initially talked about the Season Pass we mentioned making our first ever story-driven single player DLC. This is an ambitious story with strong ties into the narrative of The Last of Us. We just wrapped up a long casting process for a new character, and we’re starting our performance capture shoot next week. The single-player DLC is currently planned for release around the December-January timeframe.
Source: PlayStation Blog