It was only when a 24yo postgrad from China moved into my sharehouse that the changes to China hit home to me: due to the one-child policy, she was an only child, and she was the focus of her parents, and all her grandparents. Although a sweet girl, she was also startlingly childish and selfish. That's just one anecdote. But only children do have a tendency to be spoiled (I was an only child myself, and I was certainly spoiled).
These two experiences illustrated for me the fundamental change that is transforming China - from family to individual. I think this consequence of the one-child policy is far more significant than the gender imbalance. What will it mean?
(I apologize if I've offended anyone with this sensitive topic; it's not my intention. I'm connecting some of my own meaningful experiences with large scale changes, and I welcome refutation/refinement.)
There are ~1.3 billion Chinese, but let's assume the this issue covers 1/3 of the population. So it's (1300/3 + 32/2) vs (1300/3 - 32/2) which works out to 4350:4318. Now we might guess that there will be large numbers of men that don't ever have a relationship. But, what people forget is relationships don't always last. People die, or get divorced ect. So what ends up happening is women will spend a higher percentage of their life in a relationship and while some men will never marry this is "normal" and they can still have relationship with women throughout their lives.
If anything expect women to marry younger and female widows to be in higher demand than males widows. Granted, if the male to female ratio ever reached 2:1 there would be issues but this is still a minor imbalance.
In places like South America there is often an imbalance favoring males before age 15 which shifts over to females from age 20 onwards. It doesn't mean war or revolution -- just a lot of urban violence and early deaths of males as they compete for mates. It's not pretty but neither is it a dire international problem.