Why do u need 10 billion people on this earth?
Because every year there will be at least one true individual born
and the odds of that true individual able to live through to the
end of their lives without any mishaps and still staying true to
the path of truth are minimal.
So if you need to fill Heavens with many of such true
individuals, you will need to wait all of them to reach their final
destinations and become the person that they were meant to be in
their lives.
The Earth isn't going to end until this task has been completed
and the number of true individuals reaching Heavens have been
reached.