i think, b4 we get a robotic doomsday, we might get a environmental doomsday. worst of all, we might get a bioweapon doomsday b4 we even need to worry about robotic/AI doomsday. compare to robotic controlling humans, im more concern of bioweapon that are capable of killing targeted humans with specific DNA or specific biological attributes, or a biological weapon that can completely disintegrate a human body leaving no trace or evidence of its existence.

for terminator/matrix style doomsday, its due to human arrogance and ignorant. humans are the architect of their own demise, "the 2nd Renaissance Part 1, Animatrix". in every doomsday scenario, MAN is always the reason behind it. sadly speaking, im not too optimistic that MAN will avoid any of the doomsday they can come out with.