The PlayStation Store may have leaked that a PS4 version of The Last of Us is indeed coming out.
An advertisement appeared briefly on the PlayStation Store and blatantly showed Sony/Naughty Dog is to release The Last of Us Remastered on the PS4. Other leaks have suggested it will come with all the previous DLC released, plus of course better visuals.
Hopefully Sony and/or Naughty Dog will make an official announcement on it soon. It seems more than likely this is all true now.