I was very surprised that the world population has reached 7 billion. It is well-known that some of European countries like France or Germany and even some Asian countries like South Korea and Japan are actually encouraging people to give birth. Some say by 2040 the world population will be reduced so much that the population would be half, if not any less than that.
Have a look at this Youtube video, it explains why or how that 7 billion population is possible and it says the number will reach up to 10 billion by 2100. Then, as the video features, it will be a matter of redistribution of earth resources such as energy, power or even wealth.