Unlike when I grew up, 1950s/1960s, humans Worldwide per more recent modeling, will not all die from an all out nuclear war. Most of the southern hemisphere will survive though recent modeling shows 5 billion of we 8 billion may die in the north.
Even the worst genetically designed virus won't kill all those with food supplies in areas able to totally isolate.
Before runaway global warming occurs, humans will die off and suffer too much for that to reach extinction levels.
Natural causes like large bolides or galactic near supernovas are too rare. Long term fatal human genetic changes, given our advanced DNA science would be solved.
That leaves singularity level AI robot scenarios that yes conceivably in a war against humans are about the only possible one that could hunt every last one of us down planet wide. That scenario only works if AI could operate robot factories in countries secretly that I doubt will ever happen because that is so obviously dangerous that humans given little choice, would just totally nuke any region where that arose.
One last scenario is in the distant future, an ability to create some kind of planet wide long half life radiation cobalt bomb or group of bombs that would kill not only all of us but also all advanced life. Then yes some insane person with a finger on such a button could get us all.
So IMO, NO,unlikely within near geologic time of millions of years. Beyond that AI robots may be hard to prevent.
Also note, I doubt humans will in our present biological form ever be able to live for lifetimes beyond our planet elsewhere in the Solar System, much less for generations because our bodies are far too dependent on the Earth despite much science fiction in media otherwise. However a million years into the future, genetically modified humans or hybrid AI/humans may. David