I would say this is a near dead certainty. God only knows what's out there in terms of private letters, diaries, journals and the like but I wouldn't count on any of them surfacing anytime soon. While some families haven't been bothered by the Titanic limelight, just as many would be just as happy to see it all go away.
My guess that if there are any out there, they are in the hands of people like Louise Moss whose mother Jean Hippach was a first class passenger. Louise never would speak about anything Titanic related.