I'd say two things.
As a point of clarification, the term “irremediable” is not a medical or scientific term. It's a legal term that's been put into a piece of legislation, and in fact is defined in the law in terms of incurability and so forth, the three sub parts.
Together, the question you raised is a good one. What degree of certainty do we have to have with respect to the future in order to satisfy that criteria? I think it's going to be impossible to have absolute certainty. It's also going to be impossible to be certain in any individual case, if one were to gather group data that on average a specific set of characteristics is a certain percentage likelihood to be incurable or not. It will be hard from that average group to be certain that it applies to any one individual.
It's clear that 100% certainty cannot be what's meant by the legislation, nor achievable in any case. We're left with the question of how much certainty, and on what basis of what type of evidence do we think we have met these legal criteria of incurability, non-alleviability, and so forth.