Male-weighted populations (such as that in many areas of China, where the disposal of female children at birth was not an uncommon practice for a very long time) have a naturally more limited reproductive capacity than those that are balanced, and a MUCH more limited one than those that are female heavy. I expect an eventual decline in birth rates in those areas (though not necessarily population, due to potential for immigration from other nearby areas, etc) until the gender balance stabilizes.
As to the curves, I don't think we have really hit unrestrained growth, because TRUE unrestrained growth is the point beyond which no control is possible. We haven't hit it yet, but I see the potential, for a couple of reasons. 1) We continue (globally, if not locally) to overproduce food, so while some populations are starving, globally, we have the food production (currently) to comfortably feed about double the amount of people we have (and that capacity will, at least for a while, continue to improve). 2) expanded capacity for health care, particularly of the preventative variety, means people are living longer and men, in particular, are reproductively viable for many more years than in the past. 3) most modern forms of birth control, for some women, anyway, are getting less reliable, EVEN IF USED CORRECTLY. I have a close friend who has never had unprotected sex in her life, and has religiously taken the pill since she was sixteen... She is currently nursing her sixth son. She's an extreme case, but I hear of more and more "accidents" all the time. I am not sure to what extent this phenomenon is taking place globally, nor it's rate of acceleration if indeed there IS one (I don't even know of any studies that have been done on the topic), but it's a factor, to whatever small degree.