The way I see it becoming normal starts with adoption by the scientific minded rational atheists who are it's most natural audience. This group is going to be (rightly) skeptical unless we can do a freeze/revive round trip on a person.
I don't think that is reasonable at all. Scientific minded rational atheists who want to be the gatekeepers on this matter should be basing their opinions on the entirety of the available relevant data, not (the equivalent of) whether video tapes of monkeys turning into humans can be produced.
Even if cryonics became massively popular, however, we'd still have several problems: we don't know if we're preserving all the information, we don't know if it will ever be possible to extract the information, we might kill ourselves off first, it might never be cheap enough to revive a significant fraction of those frozen.
Frankly your analysis is one-sided. Uncertainty on this level should be making you move towards .5, not 0, you are seeing the absence of conspicuously conclusive evidence rather than conspicuously absent but expected evidence. That sort of observation increases randomness, it doesn't count as disconfirmation.
We don't know that the information is being lost (that's kind of a key point here, and yes we do have ways of telling when information goes missing, actually the fact that we don't know this is actually pretty good evidence to the contrary). We don't have any particular reason to think we couldn't extract it if it is not lost (while there are limits, the laws of physics do in fact allow a marvelous variety of things to be done). We probably won't kill ourselves off if we're careful (yeah there's a reason we worry so much, and it's because worrying works). Most expensive things not intrinsically resource-expensive tend to grow cheaper on a unit basis when there is enough demand to justify large scale infrastructure and cover initial development costs (I haven't heard a proposal for why reviving humans would be resource-expensive, as opposed to primarily an R&D cost which really seems the more natural assumption).
What I see as most promising, actually, is the continuation of low temperature medical research that has no intended cryonics application.
It's interesting that the guys who froze a rabbit kidney in M22 and reimplanted it successfully were in fact cryonicists (motivated by cryonics and funded by investors with cryonics interests), but kept their mouths shut about it in their published paper, making a big point instead about how this kind of research will be of great help for organ and tissue banking.
The trouble as I see it is that for cryonics to work optimally we need direct research on brain vitrification, so that we can minimize the damage that will need to be repaired. (We should strive as a rule of thumb to get it down to where mere engineered biology, as opposed to the more dramatic mechanosynthetic forms of nanotech, is sufficient.) Focusing on whole bodies and other organs is a suboptimal use of time for this goal except where it serves as a useful model for brains. Also banking of organs may become less of a concern from a general medical perspective over the next 50 years or so as we become better capable of regrowing tissue into functioning organs using scaffold and printing models, from a patient's own DNA.
[base] opinions on the entirety of the available relevant data, not (the equivalent of) whether video tapes of monkeys turning into humans can be produced.
For evolution we have enough data that evolution comes out as the most likely theory given the data. Without freezing and thawing a brain, how do we get sufficient evidence that we're storing everything necessary, such that "it's all still there" becomes the most likely theory?
Most complex scientific procedures need a lot of testing to get right. We can't test here. We might be lucky, but ...
Most people, given the option to halt aging and continue in good heath for centuries, would. Anti-aging research is popular, but medicine is only minimally increasing lifespan for healthy adults. You, I, and everyone we know have bodies that are incredibly unlikely to make it past 120. They're just not built to last.
But what are you, really? Your personality, your memories, they don't leave you when you lose a leg. Lose most parts of your body and you're still you. Lose your brain and that's it. [1] You are a pattern, instantiated in the neurons of your brain. That pattern is sustained by your body, growing and changing as you learn and experience the world. Your body supports you for years, but it deteriorates and eventually isn't up to the task any more. Is that 'game over'?
Perhaps we could scan people's brains at extremely high detail so we could run them in some sort of human emulator. This requires a thorough understanding of the brain, huge amounts of storage, unbelievably fast computers, and very detailed scanning. If it's even possible, it may be several hundred years away.
Our bodies aren't going to last that long, but what if we could figure out how to preserve our brains so that the information didn't decay? Then, if the future turned out to be one in which we had advanced brain emulation and scanning technology, we could be revived. I don't know if people in the future would want to spend the time or money to revive us, but in a future with technology this advanced, reviving a preserved brain as a computer simulation could be really cheap.
The most advanced technology for long-term tissue preservation today [2] is cryonics: freezing with vitrification. You add something to the blood that keeps ice crystals from forming and then freeze it. This is pretty much the same thing frogs do, hibernating frozen through the winter. The biggest organs that have been successfully brought back to working order after vitrification are rabbit kidneys, and the brain is a lot bigger and much more complex. While there are people applying this technique to human brains after death, it's very much a one way street; we can't revive them with current technology.
How much should it worry us that we can't reverse this freezing process? If we're already talking about revival via high-detail scanning and emulation, which is only practical after hundreds of years of technological development, does it matter that we can't currently reverse it? The real question in determining whether vitrification is sufficient is whether we're preserving all the information in your brain. If something critical is missing, or if something about our current freezing process loses information, the brains we think are properly preserved might be damaged or deteriorated beyond repair. Without a round trip test where we freeze and then revive a brain, we don't know whether what we're doing will work.
Another issue is that once you've frozen the brain you need to keep it cold for a few centuries at least. Liquid nitrogen is pretty cheap, but providing it constantly over such a long time is hard. Organizations fall apart: very few stay in business for even 100 years, and those that do often have departed from their original missions. Current cryonics organizations seem no different from others, with financial difficulties and imperfect management, so I don't think 200+ years of full functioning is very likely.
Even if nothing goes wrong with the organization itself, will our society last that long? Nuclear war, 'ordinary' war, bioterrorism, global warming, plagues, and future technologies all pose major risks. Even if these don't kill everyone, they might disrupt the cryonics organizations or stop technological development such that revival technology is never developed.
Taking all these potential problems and risks into account, it's unlikely that you can get around death by signing up for cryonics. In attempts to calculate overall odds for success from estimated chances of each step I've seen various numbers: 1:3, 1:4, 1:7, 1:15 and 1:400. I'm even more pessimistic: I calculated 1:600 when I first posted to lesswrong and have since revised down to 1:1000. To some people the probability doesn't matter, but because it's expensive and there are plenty of other things one can do with money, I don't think it's obviously the sensible thing to do.
(I also posted this on my blog.)
[1] Well, lose your heart and you're gone too. Except that we can make mechanical hearts and you stay the same person on receiving one. Not so much with a mechanical brain.
[2] Plastination is also an option, but it's not yet to a point where we can do it on even a mouse brain.