While the author makes a good point about how humans will never leave the solar system, there are a few possibilities to continue human legacy. Ethics aside, sending seeded capsules to a habitable exoplanet could one day (millions of years) evolve into an intelligent species. Although not human, a DNA signature or some other artifact could be engineered to validate it as a human colonization.
Additionally you could explore the possibilities of fleets of nano sized probes, which over the course of thousands of years, confirm the habitality of an exoplanet, and build a crude nursery for sperm (which could be sent at a later date). This method makes the energy/momentum problems slightly less impossible.
Additionally you could explore the possibilities of fleets of nano sized probes, which over the course of thousands of years, confirm the habitality of an exoplanet, and build a crude nursery for sperm (which could be sent at a later date). This method makes the energy/momentum problems slightly less impossible.