The Last of Us was a work of art, nothing can compare, and in fact I'm not sure they should even try. Leave it where it is and respectfully retire it. Don't try improve on it or make a sequel that can't or won't live up to it's expectations. Because there will be disappointment, that much I guarantee.
I think I agree, TLOU was really amazing, but it's been done now and I don't know if they could pull it off again now that the story's been told.
Of course, RDR is already a sequel to Red Dead Revolver....