The scenario I had in mind (which is probably more far-fetched than yours) is that (1) good life extension technology becomes available; and (2) in deciding who should get the benefit of this technology, the powers that be decide to categorically exclude anyone who has ever signed up for cryonics.
It certainly could happen - but mostly cryonics is too small to be on anyone's radar. If the powers that be decide to categorically exclude a group, it is more likely to be a larger group, and perhaps a group that is more of a direct opponent to the powers. (Also, I think you can omit (1) from your scenario - exclusion from current medical care would do much the same thing, with similar political questions, but without needing to posit a technical advance.)
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: