Only time will tell...
I think it´s an amazing game, but I see it the same way I saw the success of the movie Avatar: Avatar was the highest grossing movie ever on box office, surpassing Titanic (thanks, of course, to the expensive 3D tickets - almost double the price), but it didn´t stand as memorable on the minds of people as Titanic, which is remembered by most people even today.
I see the Last of Us the same way, it´s a masterpiece for sure, and it had excellent sales, but I´m not sure if in the future people will remember it the same way as they will remember Call of Duty or Assassin´s Creed, or GTA, for example. I don´t see the same dedication of its fans in videogame conventions like we see from fans of CoD or AC or GTA (you know, cosplays, illustrations, merchandise and all that stuff)
But again, this is just a guess, time will tell and I hope people never forget this game, making it a timeless classic.