That question's being asked all the time. To qualify for Medicare for a hospice stay, the patient's doctor is supposed to certify less than 6 months' life expectancy. (I guess it can be renewed should the patient not die.)
Two freepers posted stories yesterday involving family members in Florida hospices, though, who died far sooner than expected once admitted.
Interestingly, someone posted a link somewhere recently to the original admission form to get Terri into that hospice. There was not even a doctor's signature on it to order the admission. Very strange.