We've had a few extinction events, and I suspect even the Holocene extinction event (which is already in progress) will not be as bad as the Permian–Triassic.

Right now, three possibilities are in the running to kill off humans:
~ Climate-change induced famine and drought
~ Nuclear escalation (The US is looking at broader options... using low-yield nuclear weapons in a regional conflict)
~ AI takeover, which will likely look like the owner class developing armies of murderbots to annex the world before the AI accidentally determines they are a target as well. (And less so the Yudkowsky and Soares scenario.)

But humans are more likely to do what Homo Erectus did and go through a low population phase. They had a population less than 10,000 for millennia for a while before expanding again, only to get wiped out by competition with their cousins.

But even if humans die, life on earth will regrow across millions of years, and may even evolve intelligence and technology.