Elon Musk has stated:
Population collapse due to low birth rates is a much bigger risk to civilization than global warming
We should be much more worried about population collapse
Resolves YES if global annual population growth becomes negative and Elon is still alive.
Resolves NO if Elon dies while global annual population growth is still positive.
For the purposes of this bet, "human population" includes sentient genetically-modified humans, but does not include AIs, uploaded minds, uplifted animals, etc. However, if Elon's consciousness is uploaded (in a form that is capable of witnessing this event), that still counts as him being "alive".
1,000Global annual population growth becoming negative seems a far cry from population collapse
I think what you're describing would be better described as population peak or start of population decline
Moreover, a true population collapse would be better defined as global population halving within <50y, or multiple large countries experiencing mass death of elderly due to shortages of essential goods/services from lack of young workers