It absolutely will happen. Not only because human nature is maddeningly predictable, but because a shadow of this is going on right now. There's a bit of explanation involved.
Congenital adrenal hyperplasia ("CAH") is an adrenal gland disorder which can inhibit the development of primary and secondary sexual characteristics due to a lack of sex steroids, of which testosterone and estrogen are probably the most well known - and they also sound like the sort of thing that would be illegal at some kind of Sexual Olympics. Recently Dr. Maria New at New York's Mount Sinai Medical Center has been attempting to cure cases of CAH in utero through the administration of dexamethasone, a drug that has never been definitively tested on humans and which has caused birth defects in animal studies. You'd think that prescribing an experimental drug to pregnant women would be the height of this problem, but it goes deeper.
Back in 1999, H.F.L. Meyer-Bahlburg - apparently a colleague of Dr. New, though I've only found one website that states this, so this may be the internet echo chamber at work - wrote an article for The Journal of Clinical Endocrinology & Metabolism about CAH - specifically, one investigating why women affected with CAH have "relatively low fertility rates." From the article, it seems that CAH women "tend to have delayed (or absent) heterosexual milestones," tend not to be in relationships or marriages, have limited libidos, and "have a lower interest than controls in getting married and performing the traditional child-care/housewife role." My god.
Oh, right! They also tend to have "an increased rate of bi- or homosexuality." But don't worry! Administration of dexamethasone can fix all of this, assuming it doesn't also cause birth defects! Granted, these doctors aren't yet at the point - so far as I know - where they're administering the drug out of a desire to "normalize" outliers.
This is just one of the first whispers before the roar, to make sure we're paying attention. Once the future really hits, once genetic engineering technologies progress to a point where parents can specify the qualities of their child, it's going to get a whole lot more challenging to not be swept away with the tide.
Men and women carry the rainbow flag along Bloor Street East in the Toronto Pride Parade - July 4, 2010
It has taken centuries, millennia even, for homosexuals to even begin to climb out of the pits of discrimination they've faced in societies throughout the Western world, and outside the West the laws aimed at them are nothing short of barbaric. If governments such as Saudi Arabia or Iran, where homosexuality is punishable by death, had the technology to prevent babies from being born homosexual, they would use it. No question. Even in the enlightened West - particularly in the United States, considering the furor over the issue of same-sex marriage there - there are plenty of people who would take that option if given the chance.
I don't think they should be given that chance. I do not believe parental authority goes that far. To me, merely tolerating this notion would permit the rise of the idea that "deviance is a genetic disorder," something to be corrected so that everyone falls within the society's social norms, regardless of how outdated they may be. My notion is that the opposite of diversity is stagnation, and a society that seeks to make its next generation "normal" according to its own views is not only betraying that generation, but betraying itself.
I mean, how far does this go? Should all "socially unpopular" qualities be eradicated in utero? If there's a particular gene that predisposes its carriers to atheism, should that also be corrected? Considering that there seems to be a rather close correspondence between nations that hate homosexuals and those that hate atheists...
We need to do what we can to solve this problem before it gets too complicated to handle. My own belief is that governments need to enact what I'll call Dice Laws - a legal framework for what parents or states are not permitted to specify when designing a child. Sure, you can ask for them to be intelligent, athletic, or have long fingers suitable for playing the piano, but the direction the child ends up looking for tender companionship is not up to you. Nor should it be.
The stuff of life is not a place where we should pretend control. Not when human nature suggests people would use that control for their own interests, not those of the life they're controlling.