First step in ensuring we can survive when this planet is no longer habitable, is establishing a presence on another planet.
And when the time comes, another solar system.
And because we can. Or at least one guy in charge of a lot of related tech can. Electric cars, batteries, mass transport, rockets... Elon has most of what he needs in house.
Eventually, we won't have a choice. So I'd vote for ASAP rather than wait for public interest to die out. The mars one reality show never was viable, but got lots of volunteers. This guy seems to have a chance.