The long standing economic theory is that population growth is needed to grow the economy. A political science professor I had in college said popultaion growth of 2% was needed just to prevent the economy from contracting. I've read similar theories on this over the years. The long proven economic benefits of immigration substantiate this viewpoint.

So what happens to a world where population runs flat? The continued slow growth in the world's population you mention is fueled by underdeveloped nations in Africa and Asia, but those nations are developing radidly. There is little reason to doubt they will eventually follow the trend of other developed nations with flat or declining birthrates.

Maybe that's where AI can step in? AI holds the potential to free humanity from the need to overpopulate the planet. If it can "grow" the workforce for us we can let populations shrink to a level more sustainable for the planet. If AI does the hard work, all people can be given a universal basic income and be free to pursue their passions and lives like the very wealthy have for so long.

AI could potentially find solutions to Climate Change as well. It could develop FTL and take us to the stars. Or it could turn into Skynet and send terminators after us all.