I don't really care whether they figure out how to do that, although I don't really believe there's a "gay gene" anyhow (that's subject to revision upon further evidence to the contrary).It's no more controversial than finding out whether your child is male or female, or at least it shouldn't be. As homosexuality becomes more and more accepted (and look at the amazing strides in the last few decades - from unmentionable to gay marriage!) people aren't going to care. There are probably genetic tests that can tell you whether your kid is going to have blonde hair or brown eyes too, but people don't bother, because most people don't really care.
Frankly, I feel the same way about sexual orientation as I do about sex selection. It would be better for everyone concerned if idiot fundamentalist homophobes don't raise gay children anyhow, just as it would probably be better if sexist misogynist pigs who would abort a fetus because it's female not raise girls.
I do have to laugh at the hypocrisy, though. I'm sure Southern Baptists would freak at the thought of manipulating the genes in order to change the sex of a fetus. They'd be screaming bloody murder at the thought of altering "God's plan" in such a manner. But if it turned out that homosexuality is a gene thing, then it would be okay to change "God's plan" for those fetuses.