What will need to change is the efficiency of how we as a species make use of the earth. We can feed many times the current world population easily. We can house many times the current world population easily. What we can't accomplish is doing those things the same way we do things now.
Advances in agriculture, energy and housing are needed. Advances which are happening as we furiously type at each other.
Either we all die horribly or we'll all be fine.
Example:
> In a 1994 study titled Food, Land, Population and the U.S. Economy, David Pimentel and Mario Giampietro estimated the maximum U.S. population for a sustainable economy at 200 million
The dangers of over-population myth assumes a naive view of a static society. For instance, we can reasonably have X land for food production, from that we can grow Y food and that can feed Z people so anything above Z would be harmful. The problem is that Y is dependent on human innovation and technology. Same can be said for most resources. We never did reach peak oil.
These predictions of inevitable decline have been wrong for a long time. I don't know why you put so much faith into the modern day equivalents.