I think only a tiny minority of lesswrong readers, believe in cryopreservation. If people genuinely believed in it then they would not wait until they were dying to preserve themselves, since the cumulative risk of death or serious mental debilitation before cryopreservation would be significant, the consequence is loss of (almost) eternal life,

Humans are not totally rational creatures. There are a lot of people who like the idea of cryonics but never sign up until it is very late. This isn't a sign of a lack of "belief"(although Aris correctly notes below that that term isn't well-defined) but rather a question of people simply going through the necessary effort. Many humans have ugh fields around paperwork, or don't want to send strong weirdness signals, or are worried about extreme negative reactions from their family members. Moreover, there's no such thing as "almost" eternal life. 10^30 is about as far from infinity as 1 is. What does however matter is that there are serious problems with the claim that one would get infinite utility from cryonics.

If people were actually trying to preserve themselves early then there would be a legal debate. There is none (unless I'm mistaken).

There have been some actually extremely tragic cases involving people with serious terminal illnesse such as cancer having to wait until they died (sometimes with additional brain damage as a result). This is because the cryonics organizations are extremely weak and small. They don't want to risk their situation by being caught up in the American euthanasia debate.

What is the real probability? I think given the lack of success of humans in making long term predictions suggests that we should admit we simply don't know. Cryopreservation might work. I wouldn't stake my life, or my money on it, and I think there are more important jobs to do first.

This is one of the weakest arguments against cryonics. First of all, some human predictions have been quite accurate. The main weakness comes from the fact that almost every single two-bit futurist feels a need to make predictions, almost every single one of which goes for narrative plausibility and thus has massive issues with burdensome details and the conjunction fallacy.

In looking at any specific technology we can examine it in detail and try to make predictions about when it will function. If you actually think that humans really bad at making predictions, then the you shouldn't just say "we simply don't now" instead you should adjust your prediction to be less confident, closer to 50%. This means that if you assign a low probability to cryonics working you should update towards giving it an increased chance of being successful.

I think only a tiny minority of lesswrong readers, believe in cryopreservation.If people genuinely believed in it then they would not wait until they were dying to preserve themselves

I think you need to define your usage of the term "believe in" slightly better. Belief for what percentages of cryo success rate qualify for "belief in cryopreservation"?

If you're talking about percentages over 90% -- indeed I doubt that a significant number of lesswrong readers would have nearly that much certainty in cryo success.

But for any percentages below that, your arguments become weak to the point of meaningless -- for at that point it becomes reasonable to use cryopreservation as a last resort, and hope for advancements in technology that'll make cryopreservation surer -- while still insuring yourself in case you end up in a position that you don't have the luxury of waiting any more.