Another worry for everyone appears when even now at more or less 7.3 billion the civilization cannot achieve resources in a sustainable manner to every single person. In this scenario, a population increase per day of hundred thousands is a very bad solution to the problem.
If a couple has two or one, the population number should be maintained or reduced. However, most countries aren't understanding what's next at this rate so any government should right now start policies to control the natality.
The number of people that the World allows cannot be easily known, and it requires a sophisticated group of studies and a much more evolved economic system that doesn't permit stochastic variables causing resource loses and other interrelated setbacks in terms of optimization to distribute them respecting the regeneration cycles of Nature.
As the numbers don't provide doubts in this area and there are others like the reduction of the diversity and the need for exploitation in an unsustainable and degenerative endeavor, it's time to take measures at the international level with global agreements. Education and awareness play another vital role.