I think we will eventually end up in either a genderless society, where the sets of attributes that define gender no longer exist and humans are free to adopt whatever attributes they desire, or in a patriarchal dystopia. The dystopia will come about through "voluntary" changes that will not be explicitly forced, but will be the only option for non-men under patriarchy. The game will be more rigged than it already is.
Feminist theory has held that gender (the set of memes that people with penises behave in certain ways, and people without penises behave in other ways) is both socially constructed and socially enforced. This is accomplished by instilling a great many cached thoughts in humans of both sexes that even most rationalists never question, and then severely punishing the people who transgress those categories in a variety of horrific ways.
One cached thought in the rationalist community that isn't often questioned is that natural selection, rather than higher-level social pressures, cause certain things. If men are attracted to "more feminine" women, that begs the question of what "feminine" even means. Feminine appearance has meant several contradictory things over the course of the last 50 years alone, just as masculine appearance has meant several contradictory things. Who determines what these things are? Where do our images of femininity and masculinity come from? Who do they come from?
The technological promises of transhumanism are meaningless unless we confront and destroy gender. Gender is, as the OP suggests, maintained mostly by men for our own benefit (and to a lesser extent, maintained by women so that men will reward them). Gender socialization is dangerous because it has a hand in determining what we want, even when that is almost certainly not what we want to want.
In general, it seems strongly that some aspects of gender are social constructs and others or not. The most helpful way of distinguishing them is to look at differences across different societies. If some difference in gender behavior exists in all or almost all societies then the degree of social construction in it is likely to be small. If some gender aspect only exists in some specific times and places then it is a gender construct. Let's look at examples which are relevant to modern society. In the United States, and much of the Western world, it is ta...
Upon reading Eliezer's possible gender dystopias ([catgirls](http://lesswrong.com/lw/xt/interpersonal_entanglement/), and [verthandi](http://lesswrong.com/lw/xu/failed_utopia_42/) and the other LW comments and posts on the subject of future gender relations, I came to a rather different conclusion than the ones I've seen espoused here. After searching around the internet a bit, I discovered that my ideas tend to fall under the general category of "postgenderism", and I am wondering what my fellow LessWrongians think of it.
This can generally be broken down to the following claims:
EDIT- Due to some really insightful comments;
I replaced men being prone to aggression as a negative, with men being prone to suicide.
I made the verbiage a little more explicit that no one would be *forced* to change, but would seek out the changes that transhumanism would have available.