Assuming that we do not succumb to the threat of self-caused extinction, humans and the intelligent life that will descend from us are the only life forms with the potential to ensure that, even after the earth becomes uninhabitable, life and sentience continues. Through humans, life is developing the unique capacity to radically reengineer itself, enabling it to adapt to drastically different environments. Through a combination of bioengineering, robotics, artificial intelligence, and nanotechnology, humans will create new forms of life and intelligence which will be far more intelligent, sensitive, strong, resilient, and communicative than humans. As humanity becomes a spacefaring civilization it will further engineer our descendants to flourish in the conditions they will encounter.
After life on earth becomes impossible, it will be because of humans, and the various forms of intelligent beings that humans will give rise to, that life and intelligence will prevail.
Wherever life emerges, its evolution through natural and sexual selection probably continues in all directions until a species such as ours, with the attributes necessary to deliberately re-engineer itself, appears. While natural and sexual selection will continue in other species, once life produces an agent with our level of ability, it is upon that agent that the future of living things relies.
For life to continue to thrive after its birthplace becomes uninhabitable, evolving an agent capable of radically transforming and relocating it is probably a universal imperative. We can imagine other places in the universe where life might have emerged but either failed to follow an evolutionary trajectory resulting in such an agent, or alternatively, gotten as far as humans are presently, but succumbed to one of the existential threats we ourselves now face. Life, at least in that location, would be doomed to extinction.
Life, engineered to withstand a challenging journey and adapt to new homes far from the earth may be radically different from life as it presently exists and may not be biologically based. The life forms that will ultimately descend from humanity will probably be an astonishing variety of beings and machines, biological, non–biological, and various hybrids with attributes and abilities far exceeding anything produced by natural selection.
The crucial role that humans can play in the ultimate continuance of life is a profound responsibility. It took billions of years of evolution and a series of unlikely events for humankind to emerge. If humans fail to overcome the existential threats we now face life may not be able to produce another agent with our potential before it becomes too late.