They will be based, not on silicon, but on carbon, neurons, elements of life. Those who think so could be unaware of what machines already do. Computers can recognize faces. Computers can understand continuous speech. Computers can compose in the style of Bach.
Computers can improvise jazz.
Computers guide missiles, pick stocks, diagnose electrocardiograms, discern types of cancer, prove mathematical theorems, write poetry, play ping pong, make up jokes. That's sometimes disputable. Missiles can go awry. Jokes can fall flat. Computer-generated trading is blamed in large part for the 1987 stock market crash.