There are historically other paths that science and technology have taken in the past in different industries, and to ignore these alternate possibilities seems rash:
- Chaos: The study of weather in the 60s(?) promised to allow long-term weather forecasting so that we could all schedule our picnic outdoors 3 months in advance and not worry about rain. Then chaos theory showed us why this is more or less an impossible thing to predict in the long term.
- Large Capital Cost: The Apollo missions ended with the Cold War. Things may eventually change, but space exploration, especially manned, has reverted. We haven't been to the moon in decades.
- Physical/Social Danger: Nuclear Energy promised to give us unlimited cheap clean energy forever. Instead, there has been no new nuclear power plants built in the US in about 15 years. Chernobyl, concerns about Yucca Mountain, public dissent killed off the nuclear industry.
Who knows what the future will bring.