I wouldn't expect that. After all, the Danish RF don't usually share tiaras and each lady has her personal tiaras to wear. I think that Margrethe will keep to or three of her tiaras for personal use, and making some others available for Mary. Strictly speaking, the ruby parure is Frederik's property, as he inherited it from his grandmother Queen Ingrid. So it's not bound to the position of Crown Princess. I can imagine that Mary will continue wearing it for life, while Christian might inherit a tiara directly from his grandmother, Queen Margrethe.