If you have not played The Last Of Us yet or at least made it about half way through I would recommend not reading much more or even watching the clip below as it does link up to one of my favorite parts of Ellie's past. That part being where she talks about how she survived with her friend only to have her friend get infected and forcing Ellie to go solo. While there isn't much detail on what we will be getting in this new DLC I think with what is shown below we can assume it has much to do with this part of her past.
I am not normally one of for DLC in games, but when it comes to adding a bit more to the story of The Last Of Us I am all gung ho for it. All of the main characters in this game were so well written and portrayed I know I ended the game wanting to know more. The Left Behind DLC is hopefully the first in the expansion of this. There is so much to the story still left open and I personally hope this does well and keeps Naughty Dog churning out a bit more to add to it all.
Now we just have to wait until we get a better release date than 'coming soon' for the Left Behind DLC for The Last Of Us. I am guessing early 2014 personally. That is based on them still stating 'coming soon' before December mainly. We'll see. At least we have the Multiplayer and that DLC to keep us engaged until then.