I’m not going to gamble on his death. Besides, who was the last president to die in office other than assasination?
FDR. Others who died from natural causes are William Henry Harrison, Zachary Taylor, and Warren Harding. None of them were 72 when they took office, or had cancer.
Its not exactly a gamble. McCain WILL be the nominee, unless he dies, strokes out or some huge and as yet unknown scandal goes public (maybe he's Client #10?). Being the nominee, he WILL choose a Veep. That's about all there is for us conservatives this time around. You fight the campaign with the Party you have, not the Party you wish you had.
The last President to die of natural causes in office was FDR. He was quite sick when reelected in 1944, something that couldn't, I believe, happen now. However, McCain will be the oldest President ever to take the oath, and he is not in the very greatest of health. I wish him good health and a long life (like his still-living mother, age 96), but one must be a bit realistic. His chances of survival go down each day (as does everyone else's).
Note that Nixon didn't die in office - physically (though politically is a different animal). But he was forced out, and his Veep took over. That is unlikely, but also another reason to put in a conservative Veep.
Finally, whoever is the Veep will have a leg up for the next campaign that doesn't feature McCain (though Fred Thompson likely won't run in 2016 - too old, and he's not the type to spend his old age in a job like that).