I don't think we'll go extinct because our planet is still pretty big but I certainly think a cluster fucked Fallout style scenario is entirely possible. I'd agree with either Bio weapons or nuclear, it also won't matter if it's a private organisation or state for me because it all it takes is for a few batshit crazy people to have the launch codes and we're screwed but I voted state because they tend to have the most insane and corrupt people.
We'll still survive, but chances are it will be on the outskirts of civilisation and away from the major cities because those will be the first targets by whoever decides to launch the weaponry, I think the Fallout game minus the ghouls is a pretty realistic depiction of life after Armageddon.
Kinda agree