"Humans, who are limited by slow biological evolution, couldn't compete and would be superseded"
This is no bullshit and a very plausible scenario.
This post brought back fond memories of my two favorite movies: iRobot, and Matrix trilogy.
Artificial intelligence does have the potential to make computers smarter than humans and (God forbid), possibly try to exterminate us because we are an inferior species. We are still a long way from creating fully autonomous AI. It would require massive processing power and perfectly written software. Personally I don't think it can be fully autonomous because any software program can be taken apart by whoever wrote it.
I saw one of the commenters (HorsemanUK) mentioning evolution with respect to computer code. He hit the nail on the head because what these scientists are actually afraid of is that one day computers might decide that they don't need us (humans) anymore. It sounds like it belongs in a sci-fi movie but I think it really is a possibility.
One more thought: is it even possible to program human emotions into computers and make them understand? Some of the most basic human attributes like compassion, reasoning, motivation, etc. are virtually impossible to program into computers. How can computers take over the world if they can't even understand who/what they are?