i find it unethical NOT to tell the truth to the patient or power of attorney, While an actual number of days can rarely (and reliably) be 'predicted,' an eventual outcome likely can. This MEDICAL OPINION needs to be put into perspective however.
Then, it is the job of the family, the same physician, friends and everyone, social work, chaplaincy; that that is the MEDICAL OPINION.
That said, (that the physician has just given the MEDICAL OPINION, that doesn't discount the valuable input of hope and faith and miracles. They must never be discounted. This is where the physician, family, neighbors, friends come together for the best outcome.