First, some clarification on the one-child policy:
* members of ethnic minorities are allowed two children
* if a husband and wife are both only children, they are allowed two children
* even if not 'allowed' more than one child, in most instances that means simply that you pay extra money for subsequent children (something that many affluent families are happy to do, although can be a significant burden for poor families)
In addition, the Chinese gov't has been slowly loosening restrictions around the one-child policy, and has plans to continue to do so.
However...they still plan to keep a tight control on population growth. They may relax restrictions to allow two kids, but are gonna' keep a tight cap on anything more than that.
And as much as I dislike it, I agree with it. There was discussion above about how many developed countries are experiencing significant decline in population growth, without the need for such policies. In general, greater affluence tends to lead to lower birth rates. And this is happening in China, too...wealthy urban families are tending to feel far less pressure to have kids, and have a preference for only one or two (or in some cases, choose to have no kids at all).
But in poor, rural populations -- which still make up the majority of the Chinese population -- the desire for large families is still very strong, and despite gov't efforts to control the number of kids, many rural families will still have as many kids as they can.
The problem with this is that it essentially perpetuates an endless cycle of poverty. Because they have many kids, they don't have enough money to provide adequate education. The kids grow up to be pretty much exactly like their parents (and numerous studies in China have shown that poor families who have fewer kids rise out of poverty faster than poor families who have many kids), stuck in poverty and having lots of kids in turn.
Urban families have a lot of money, which is spent on only one or two kids, providing significant resources; rural families have little money, which may be split between three, four, five, or even more kids.
Education is a huge factor (in particular, making rural families understand that smaller family size does lead to greater opportunities to escape poverty); but it is very slow, and fighting thousands of years of tradition that "large families equal stability and security".
My position is that laws to limit the number of children are still essential; but the question of how many children should be allowed, or of how to enforce such laws, is a much trickier one, and I don't have any easy answers.