Whoa. No one expected this.
The Last of Us has more story to be told, and enough content to be put into another game. Naughty Dog was very hesitant of making this decision because it was such a loved game when it came out in June 2013. The campaign ended very well, and didn’t need much explaining after it. Now, ND has shown us that there’s more to it. There’s nothing better that we could ask for (Except for another Jak and Daxter or even a remaster of Jak X)!
Not much is shown, but it’s very, VERY beautiful and in the distant future, approximately 5 to 10 years after the first game. Ellie is older, way different-looking, kind of like Tess from TLOU 1, and Joel isn’t really shown. The front half of him, that is.
Go and check out the eeriness yourself and guesstimate upon what the story could be about this time.