Postgenderism is the belief that with the aid of technology we can "transcend" our gender. With the rapid change and improvement in genetic engineering the act of sex could be looked upon as an unnecessary biological danger.
Not only would the act of sex be looked down upon as an unsafe practice, but there will be a push for the merger of both sexes, to create a fully asexual being.
Aaron has covered this as well in his post On Marilyn Manson (posthuman)
Why continue the spread of undesired genetic strains of man, when, for the first time humans can now be designed, and the creation of the perfect man becomes possible.
This will be the mantra of the eugenicist/geneticist
What about the pleasure that comes with sex you say, well all that can be simulated in virtual reality. Think of all the sexual crimes that can be eliminated with the ability to simulate a sexual experience that feels, looks and even tastes real..
Now considering we began by exploring postgenderism, it seems likely that virtual sex with male and female would preceed the creation of the posthuman. The reason being that the posthuman may develop to a point that it has no need nor desire to interact with a human male or female.