I find it hard to believe we would reach 50 billion people within the next millennium without new and incredible resource extraction technologies that would make current food shortage problems look like a piece of cake.

Resource extraction... sure, but I think the issue is more that there will be no resources left to extract at some point. We are already wasting a lot of things, even something as basic as water.

What water? None of it leaves the planet. If you want enough clean water, build a nuclear reactor and hook it up to desalination plants.

What predictions? If you believe in scientific modeling at ALL. AKA you think global climate change is scientifically sound, then you should probably look at the population growth predictions.

https://en.wikipedia.org/wiki/Projections_of_population_grow...

Most likely global population figures are reflecting the sign of the times. There was a period of 'irrational exuberance' between 1998 and 2004 where the 2100 projections suddenly dropped to as low as 8.4 billion, but after that we have been reverting to the projections of the 1980's and 1990's of 11B+.

I just clicked that link and all of the projections were aimed up, even if slowed. Current projections still put 11.8 B people by 2100.

There's plenty of places where you can live pretty much on your own, even in the US. Crowded cities isn't caused by too many people on earth.