I would also surmise that most the people who desire the current two-gender system to persist are men (and therefore used to being the dominant gender, and therefore not personally feeling a reason to change it).
Although this may be true, I would be very surprised if more than 5% of the population would want to eliminate the two-gender system. If you were trying to campaign for a single gender, you'll have to focus on appealing to both genders.
As for the one-gender society question, current social values indicate it will be a century or two before this idea could seriously enter the mainstream views of the world.
For the foreseeable future, I predict the slow decrease of gender roles in society.
I am not arguing that people would start out TRYING to eliminate the two-gender system. I think it would happen naturally as people first got rid of maladaptive differences (aka- aggression, low social skills and low empathy for men; and depression, low risk-taking and low self-promotion for women), which then started a cycle towards one-gender or similar
In other words, one gender (or low gender differences) isn't the original desire of anyone. It's the unintended result.
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.