I'm struggling to think of a task that a machine cant or wont be able to do. I cant get further than art and thinking up things for machines to do, but even then I'm not so sure. I'm sure even philosophical issues could eventually be determined by a computer program. Robots can perform most mundane tasks, and equally highly complex tasks we cant even do. We even have machines that design and build machines.
So yeah, offices will be a thing of the past, because workers will be a thing of the past. Well, just a few workers who watch over the machines. But, wont they be deemed inefficient?