For machines to become more important than humans from an evolutionary standpoint (which is all that matters actually in terms of species extinction), then they must become alive and that means they must have a bell curve of attributes and have failure. Because without failure, there isn't existence of life (the past and future will collapse into undifferentiated without friction and imperfection).
Of course, and there's nothing inherently impossible to that. On the contrary. What makes you think that machines won't "come alive", have bell curve distributed attributes and have failure (I'd say that if there's one thing they already have, is exactly that !) ?
What happened to carbon chemistry, can just as well happen to silicon. I even think it is unavoidable. If it can happen, it will, because it not happening is simply unstable. Like an oxygen-hydrogen mixture not exploding. It is simply waiting for a spark.
I'm of course NOT thinking of a centralized production of clones, Star Wars style. I'm thinking of machines all over designing new machines, different ones, each of them improving over others (in the beginning, based upon human demand !), in a competitive warfare. Just like the first carbon life forms proliferated, differentiated, and battled amongst themselves. Once they outsmart us, are everywhere, and indeed, are all different, I don't see how they will not overtake. Like we overtook the biological world and became a dominant species.
My idea is that anonymous cryptocurrencies are part of that evolution. Indeed, what makes humans immensely powerful over other species, is their economic cooperation. Economic interaction is the way to bolster the power of collectivity, while retaining the flexibility of individuals. Communism, like ants, has its power, but is also limited by its centralization. Individuality, like leopards, limits the power to the abilities of single individuals. Economic interaction takes the best of both worlds. So as long as machines cannot have economic interaction amongst themselves, we, humans, will be superior, because even an individual smart machine cannot win against the human collective. However, once machines can start their own economic collective, with their higher intelligence, we've lost that superiority, and they will become vastly more powerful. In order for us not to see that, and in order for them to be able to do so, anonymous crypto currencies and smart contracts are what is needed.