Singularity. Faster machines making faster machines. End of the line for us.
When we are talking about machines becoming faster, what do we mean exactly ? If it's merely about computing power, then it's faster calculators doing faster calculations. Nothing new there, even the earliest vacuum tube-driven computers did it faster and more accurately than any human could, which was exactly the purpose of having them. Unlikely that calculators would cause the end of the world.
Then, although I don't believe in AI being in any sense "intelligent", for the sake of this argument let's pretend we had already crossed this unimaginable gap between a thousand linear equations and self-consciousness, and our calculators have become intelligent. Then the singularity argument becomes that faster means more intelligent and that smarter computers keep building even smarter versions of themselves, and it accelerates exponentially.
Now we have to face a bigger question, as to what exactly we call intelligent. An impossibly large question in itself, but in the context of this argument we could reduce it to the question of independent will.
Unless we associate intelligence with independence, our more intelligent creatures are limited in that we still can program (sic !) them or at least predict their activity. Then it's a really low cap, definitely not capable of exponential growth. Controlled by humans, still makes them little more than savant slaves.
And if we agree that intelligent computers would become "like humans only smarter", in this act of anthropomorphic creation grant them free will, then we ought to give up all hopes of predicting or even reasoning about their actions. Especially given that they are designed from the outset to be more intelligent than ourselves.
Finally, to conclude the argument:
What makes you think that independent creatures infinitely smarter than us would do as we did and create smarter versions of themselves ? And that they would set to do so right away, and not after 2 billion years, having had a good thought ?