If you look out far enough the computer will eventually learn to reason in somewhat the same way that humans do, so called ‘artificial intelligence’. If you take that far enough you can imagine an evolution, essentially, moving over to silicon-based life and carbon-based life, playing a much more limited role than it does today.
Gates is speculating about the long-term development of artificial intelligence and the possibility that computers could eventually acquire forms of reasoning resembling human thought. He presents this as a distant prospect rather than an immediate prediction, imagining increasingly capable machines as part of a broader technological progression.
The second part of the quote moves from computing into a more philosophical thought experiment. By contrasting silicon-based and carbon-based life, Gates considers whether advanced machine intelligence could one day become more prominent while biological life plays a reduced role. The passage therefore concerns both the technical ambition of artificial intelligence and questions about the future place of human beings in a world of increasingly autonomous machines. It can be used in discussions about machine cognition, technological evolution and the long-term consequences of creating systems capable of reasoning independently.