The main problem with Pascal's Wager isn't that the odds of winning are tiny but that it unduly privileges a particular tiny possibility. Perfectly straightforward expected value calculations will tell you that you should follow Pascal when you feed them "eternal bliss" as a possible reward -- if you ignore all the points in metaphysics-space besides "generalized Christianity" and "business as usual".
It's a lot harder to argue that the space of cryonics outcomes includes some hidden options that the expected-value result doesn't address. I have occasionally seen people speculate about a sadistic future that wakes cryonics patients up and tortures them for fun, but that seems rather far-fetched.
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.
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: