Yes, that is precisely what we will do. The fastest-growing sectors of the US economy are information technology and health care. I can think of several other lucrative industries that are on the horizon as well: Biotech, solar energy, nanotechnology, etc. And even more important are the ones that we aren't even thinking about yet.Second, there's a limit to how many jobs can be displaced, and we're just about there. A few hundred years ago, nearly everyone worked in the production sector of the economy. During the Industrial Revolution, a bunch of those jobs got taken over by technology, and the workers were displaced to the manufacturing sector (resulting in a bunch of unemployment in the transition). Then, during the first part of the 20th century, workers started to get displaced from the manufacturing sector into the service sector, which was one of the big contributors to the Great Depression. Now, the service sector is the biggest economic sector, and it's started to be phased out. Where are the workers going to go now? Are we going to invent an entirely new economic sector for them?
If you consider them useless, and if you consider having a useful job to be an important factor in your employment, don't work at them. Go be a farmer (with the assistance of a tractor, fertilizer, and all the various other manufactured products, of course). But just because you personally deem those jobs useless is no reason for our society not to pursue new technologies.Also, notice how the importance of each new sector has decreased. The production sector produces the basic necessities of life. The manufacturing sector produces technology and allows our modern standard of life. The service sector is largely a matter of convenience. How irrelevant would a fourth sector of the economy be to actual life? Do we really want to force people to work at such useless jobs just to survive?