I wouldn't count on it. Even if it were possible the genetic pool is too vast for single traits to really have an impact. Plus consider that most (if not all?) homosexuals have heterosexual parents - that is more influenced by number children, but it shows that there is more involved than just people who have the traits being selected out. Most of the biggest advocates against religion were born in religious families. Most parents regret having kids, most couples who have kids are less happy than couples who don't have kids. People wanting to be child free is here to stay and it will grow before it has any chance of being bred out. Choosing to be child free is the rational thing to do if you want to be happy. I welcome people to join more people avoiding having kids here: http://reddit.com/r/childfree
In case of homosexuality it could be that the genes which cause this in a man are also helping his sister in becoming more attractive to other men (and the brother of a homosexual woman to be more attractive to other women).
I have no stats on this, but it would be interesting to see if the sisters of gay men and the brothers of lesbian women do have more kids than the average (for the same education and income levels, of course).
There is a Italian study that shows mothers of gay men are quite a bit more likely to bear many children than mothers of only hetero children.
Their conclusion is there at least a partial genetic component, likely coding for "Likes to have sex with men" that the gay men just happen to get as a side effect of the very effective gene for women.
