It's quite possible that parents would in retrospect, 20 years later, regret picking a boy over a girl, if so does everyone else. However, given that the sex imbalance persists in Chinese kids born now (whose parents are aware of the gender imbalance, but are perhaps overconfident due to survivorship bias† or focused on other factors), I'd say that a tragedy of the commons is quite possible. If the technology were cheap and universally available, I suspect you'd see something like 3 boys to every girl.

† That is, of course their little boy will successfully find a wife when the time comes, just like his daddy did!