Exactly! in the future, One can build robots or artificially intelligent machines that can travel and make some decisions on themselves. Such machines will not need most biological conditions needed for organic life to survive. So can live in many hostile conditions.
They can also clone themselves mining the resources and energy available at anywhere they land.
I think the actual feasibility of man made annihilation is smaller than what it is made out to be by the media and entertainment industry. The two most popular ways that are highlighted are nuclear war or bio-engineered pathogen. As far as the first one goes, nuclear war will only eliminate the population centers and irradiate everything, there would be survivors and they would adapt to the conditions.
The second, a pathogen, is just as unlikely to get every last one of us. A virus with a 100% kill rate is highly unlikely. Look at Ebola, while weaponized Ebola would get a great deal of us it's kill rate is somewhere in the 90%'tile, I don't know the exact number but I know it is high and I believe that it is the highest. 10% of the earth population is still allot of people. Even if it is less than that, somewhere their will be a group of people that for whatever reason are resistant to the pathogen.
The only thing that I think is a real threat to our existence today, is a big piece of something floating around out there, deciding to slam into us down here. I don't think we have the capability to do it to ourselves. I heard someone say that it is likely that we will keep resetting ourselves back to the stone-age at a certain mark in technological progress, which I think is a little more feasible, but I personally believe that mans desire to cull different people is self regulation for whatever reason.
They can also clone themselves mining the resources and energy available at anywhere they land.
Such machines can colonize the space.