Actually I suspect that we would have to find a way of "de-programming" the reproductive imperative. After all, all such things have to be in the genes somewhere and I suspect we would have to find the genes to fix that particular problem. We should not underestimate how strong the drive is to pass on our genes (says this confirmed bachelor who decided long ago, without regret, that he didn't want to contribute to the world population
) and we should also not underestimate our future ability to control our genes in almost any way we choose (which is of course a whole other topic for debate).
With regard to sexuality, I'm not quite so sure about that one. I think it was in Anthony's thread that someone brought up the topic of the menopause which was brushed aside as something our future technology could fix. However there is a big problem there; as I understand it women are born with a finite number of ova and that's it, I suspect it would take some major work to change that and probably not desirable anyway given the need to control the population. More likely that on maturity men would have their sperm frozen and women their ova, before being sterilised. Conception would then be exclusively through IVF (probably much simpler than reversing sterilisation) and it is quite likely that natural pregnancies would be voluntary and very rare. Given all that would we still be interested in sex after say the first 100 years or so? And if we were having removed the family producing aspect of it would it necessarily continue to be something tied to relationships, no matter how short or long they were.
On the cost front I would agree that cost would be likely to come down but in the interim how many would die "unnecessarily" and how much resentment would that generate. Also it might be an ongoing cost requiring repeat treatments. I am reminded of Pratchetts Strata where the currency in use was "days of life".
I would like to believe in the utopian ideal of a world where energy and robotics are abundant and people no longer need to work but looking at our history, as technology has improved and replaced workers the only result has always been poverty and third class citizens. I am just not confident that we will ever achieve such a world, apart from anything else it would not be in the interests of those with the most wealth and power. OK so maybe I'm a cynic but there you go.
Your point about property is interesting, I had not really considered that one and I think you are right that owning property would probably become something well beyond the means of most, perhaps all, private citizens. Instead maybe all property would be owned and managed by funds into which private people would invest (after all we seem to be moving that way already).