At first I was going to say starvation/not enough resources/overpopulation. But then I thought it’s unlikely humans would go completely extinct from that, there would just be a huge reduction in population and there would then be enough resources for the survivors.
Then I thought war, but honestly, is anyone really stupid enough to start a nuclear war? Every country must know that if you nuke another country, you’re gonna get nuked yourself.
Artificial intelligence/technology is possible I guess, but there’s a pretty simple solution for that: Asimov’s Three Laws of Robotics (http://en.wikipedia.org/wiki/Three_Laws_of_Robotics). Of course it’s unpredictable what will happen after we reach the inevitable point where robots become smarter than humans (http://en.wikipedia.org/wiki/Technological_singularity), but I like to think that part of gaining higher intelligence means realizing that violence is stupid and pointless. So I doubt superintelligent robots would see any reason to destroy us.
Disease/epidemic is unlikely I think. Kind of like starvation/not enough resources/overpopulation, it could very well take a huge chunk out of the population, but probably not get rid of us entirely.
The rest are all either too vague, too far in the future to be able to form a reasonable hypothesis for, or too random/arbitrary (e.g. of course a meteor of species-destroying size could potentially hit at any time, but it hasn’t happened in millions of years, so why should we expect it to happen any time soon?)
So I guess I would have to conclude that humans will in all likelihood be around for quite a while yet. As for industrialized society as we know it? Not so certain…but I guess we’ll cross that bridge when/if we come to it.