I think you make a good point, but if the probability of cryonics working is sufficiently low, then relatively speaking, there are a lot of bad outcomes which are not far-fetched. For example, religious fanatics taking over the government and denying life-prolonging medical treatment to people who had previously signed up for cryonics.
Is it really even as remotely likely that religious fanatics will take over and then do that as it is that cryonics would work? (I would think that discriminating against cryonicists, when no religion I am aware of has any real official anti-cryonics position yet, would be something like a billion places down on their TODO list.) Or are you just privileging the hypothesis?
From Mike Darwn's Chronopause, an essay titled "Would You Like Another Plate of This?", discussing people's attitudes to life:
Conclusion, graphs, and references in article. As usual, I recommend reading Chronopause.com as Darwin has many good articles; to quickly link a few: