Interesting question that raises some really thought-provoking ideas about nature v nurture.
Another questions is what point in our DCs lives are we talking? For example, my parents (both dead now) may have been fairly disappointed with me in my mid-20s due to somewhat hedonistic lifestyle I was living and then I made it worse by shacking up with an abusive man. However, fastforward to my life now and I am very much a product of my parents values and upbringing and I know they would be proud of me. There were values and attitudes of theirs that I totally rejected during my 20s but I have fully embraced them in my 30s, now that I have children of my own.
I have come to recognise that I am more my parents child than I ever realised.
I accept that different factors are involved for children with SN, and that there are always exceptions to every hypothesis. I also accept that the infludence of society (particularly peer group) cannot be underestimated and that the element of personal choice (to choose or reject your parents values) is also very significant. You cannot make sweeping statements and expect them to apply to everyone. However, as a general rule (how's that for a sweeping statement! ) I think a great many people grow up to reflect their upbringing.
TheArmadillos comment earlier about WifeSwap was interesting. IMO, however, that kind of behaviour is preventable. 4 teenagers behaving like that are being allowed to behave like that. In RL I see other mums with much older children than mine (I left having mine a good 10 years later than most of my friends) moaning about the fact that their kids do nothing around the house, but it is precisely because these are the same mums who have taken great pride in 'looking after' (i.e. doing everything for) their DC. The DC have never learned to look after themselves/do their fair share around the house.
I don't really think about my own DCs futures and how they might disappoint me. I tend to focus on things that I want to give to them. If like me, they are left without a mum at 18, I hope to have done my job and armed them with a moral compass and enough self-reliance, self-esteem, compassion, self-discipline and freedom of thought to make their own way in the world.