I agree that the first part of that may well be true -- it was (b) in my last paragraph -- but I'm not so convinced by the first bit. My own evaluation is that most of the probability mass of "cryonics fails for me" involves things going wrong after the end of my life, and while I would indeed very much prefer our species not to go extinct soon after my death, knowing that it will wouldn't stop me caring how comfortable my retirement is, or even caring how much money I'm able to leave to others when I die.

Actually, I'm skeptical of this sort of argument whichever way it goes; my (b) was more a concession to those who think differently than anything else. My preference for the next (say) 20-50 years of my life to be more comfortable isn't materially altered if what follows is going to be infinite blissful heaven, or if it's going to be infinite tormented hell. (Whether the heaven/hell in question are technological or religious or whatever else.) So if cryonics is unnecessary because we all win anyway, I would rather not spend any money preparing for it.