We are now but if humans go back to the stone age because of a world war or something, we may not have a second chance. The people after us will have none of the same advantages since we extracted all the easily accessible fossil fuels that made the industrial revolution possible.

If you aren't worried about humans per se, a billion years is probably enough time to regenerate fossil fuels and evolve another technological species from scratch. Probably quite unlikely, but still. It's a very long time.