I bet with current knowledge and technologies, humanity could afford to lose 99.999% individuals, and the remaining million would still be better off than those primordial 10 thousand. Society is not likely to collapse.

There's a line of thinking that if we backslide far enough (i.e. lose the Internet, lose electronics, and lose electricity generation), there's no coming back to this point. The industrial revolution wouldn't have happened without easy-to-extract coal and oil. Today's reserves require a fairly high level of technological advancement to access.

For what it's worth, I don't think that humanity is going to hit that point of no return.