No. The burden of proof lies with those who argue against the right of mentally competent terminally ill patients to be cryopreserved if they so choose. To quote the American College of Physicians Ethics Manual:
Each patient is a free agent entitled to full explanation and full decision-making authority with regard to his medical care. John Stuart Mill expressed it as: “Over himself, his own body and mind, the individual is sovereign.” The legal counterpart of patient autonomy is self-determination. Both principles deny legitimacy to paternalism by stating unequivocally that, in the last analysis, the patient determines what is right for him…. If the [terminally ill] patient is a mentally competent adult, he has the legal right to accept or refuse any form of treatment, and his wishes must be recognized and honored by his physician. — “American College of Physicians Ethics Manual. Part II: Research, Other Ethical Issues.” Recommended Reading, by the Ad Hoc Committee on Medical Ethics, American College of Physicians; Annals of Internal Medicine, July 1984; Vol. 101 No. 2, pages 263-267.
The fact that we live in a world where the terminally ill cannot choose cryopreservation as a legitimate medical treatment prior to their legal death says we live in a world with laws that are inconsistent with the ethics prescribed by the American College of Physicians Ethics Manual.
Another way of answering the question is the following: if cryonics works, failure to comply with the wishes of a person who chose cryopreservation will result in certain death. On the other hand, if cryonics does not work, cryopreserving patients following their legal death (which is the current practice) injures no one; and even complying with patients’ wishes to be cryopreserved shortly before their legal death (should such become legal in the future) would only be done as a last resort to save their lives, and only when they had little life left to lose, either in quantity or quality.
Given these facts, someone who argues that cryonics does not work and that people should not be allowed cryopreservation as an available option must bear the burden of proof, for if they are wrong, their error could consign to death those who wished to choose cryonics but were denied that option.
See also the question Where does the burden of proof lie when attempting to determine the scientific truth of a proposed claim, such as the claim that cryonics will work? (the second question in the Scientists’ Cryonics FAQ).