HE didn't refer to her as ''sakura-chan'' just 'sakura', there is not meaning behind it even if he did call her that , it would be only for nostalgia purpose if he did happen to mention her as sakura-chan. Either way Naruto and Sakura having romantic feelings for each other are out of the realm of possibilty now, the both have families now, so it would be best to just let it go. Both Naruhina and Sasusaku suck but it's best to focus on the children now and their relationships, and not the 'old' pairing ships anymore because in the end it's futile and irrelevant to this upcoming story.
I know he didn't call her chan. People were just bringing up that Naruto didn't call her that anymore and I was confused. And yes I agree. Despite Naruto smiling when thinking about Sakura, I don't believe NS still has a chance in hell.