There is a finite amount of land, and the supply of food is less than the demand. People are more and me frequently not having children. We are also due for a war and it seems one is imminent in the middle east with Iran focusing on developing a nuclear bomb.
As prices continue to rise, people are choosing to have smaller families than ever before. In addition, multiple children are no longer needed to help work the family farm or business, and infant mortality rates are lower in western countries, which eliminates the need to have many children to guarantee that some survive.
No, the world population is not about to start shrinking, because people will always continue to procreate at a fast rate, it's just what people do. Also, as technology progresses, people will live much longer, which means those 'already here" will continue to be here longer, creating more of a population concentration.
In recent years, a lot of important steps towards better family planning have been taken, but that does not necessarily mean that the world population will start to shrink just yet. Medical advances have kept the elderly alive for many more years, and given countless children who would have otherwise not survived a life of their own. While this isn't bad, it does mean that fewer and fewer humans are leaving, even as more are being born. Recent advances in quality of life, like having proper food and shelter, have also contributed - people who could only afford to care for themselves in the past, or who would have otherwise died, are continuing to live. With the death rate so drastically changed, I do not think the population will be shrinking soon.