Actually, the science for cryonic preservation is advancing. Don't forget, there are thousands of people walking around today who, as embryos, were frozen in LN2 for years. Although there have been no successful resuscitations for frozen mature individuals to date, you really can't prove it can't happen. There's nothing in physics that says therapies can't be developed to repair cells (they don't burst, they dry out). There's just nothing in medicine yet for it.