Yeah, it's one of those things that are kinda' important to remember when talking about future developments in automata -- while humans are pretty good at a lot of things in a subjective sense (relative to other "natural" entities), we're really kinda' terrible at most everything in something approaching an objective sense (from the perspective of maximal efficiency or effectiveness). There is basically nothing a human can do that a machine will not, eventually, be able to do better, and, in all likelihood, cheaper (though that usually comes a fair amount of time after the better side of the equation).
And that holds true for pretty much everything else. Evolution is kind of a terrible engineer -- really good at what it does, but really bad at actually achieving goals beyond that particular focus, solving problems, etc. Machines -- AI, expert systems, simple automated systems, whatever -- are almost certainly going to eventually replace... well, basically everything. Because they're better at it (it being whatever task or tasks are being considered) than we can be. Since they're, y'know, specifically built for it, whereas more or less nothing else is. Barring some kind of catastrophe or specifically sabotaging ourselves in that arena, the question of humans being effectively replaced in all roles is not a question of if, but when.
... and we kinda' want that to happen, imo. Means we can goof off, do whatever, and still avoid starving to death in the streets. Probably. It's certainly a greater likelihood of success than pretty much any other scenario for eliminating human suffering. Chance of robot apocalypse, sure, but at least in the scenario of a robot apocalypse there's (probably) a legacy left behind, as opposed to all the other sorts.