Humans are not likely to go extinct anytime soon - anything that can wipe out the most adaptable and one of the most numerous and widely distributed species - would leave the Earth uninhabitable to pretty much all higher life forms.
That doesn't mean we can't trash the place or experience massive drops in population.
There does appear to be hope on the higher temperature corals, but I don't know of any plan to actually plant reefs like that. Australia, which benefits economically from tourism to the great barrier reef should take a serious look at it:
https://www.theguardian.com/environment/the-coral-triangle/2...
I don't see us doing that to ourselves. Climate change won't accomplish that, nuclear war won't accomplish that, biological warfare gone wrong wouldn't likely accomplish that.
I just don't see it happening. That doesn't mean it's impossible.
Anything above around 7 degrees of warming puts the human species itself at risk. Above 3 degrees civilization falls apart. Both of these are within range of possibility in the lifespan of children born today. All it would take is a few more Trump-style presidencies.
I think the OPs point is even then there would still be enough humans around to keep the species going. They probably wouldn't have todays technological benefits, but a few thousand humans could probably survive.
That doesn't mean we can't trash the place or experience massive drops in population.
There does appear to be hope on the higher temperature corals, but I don't know of any plan to actually plant reefs like that. Australia, which benefits economically from tourism to the great barrier reef should take a serious look at it: https://www.theguardian.com/environment/the-coral-triangle/2...