To the extent they actually are trying to escape, they're idiots, since making any other planet (Mars) habitable is way harder and more costly than dealing with climate change. The Earth will retain a breathable atmosphere, shielded from radiation with surface liquid water and life that can adapt to a warmer climate. There's no realistic climate scenario in which Earth becomes Venus. That would require a far worse run-away greenhouse effect than has ever occurred on this planet. Most likely Venus had massive ongoing volcanic activity that surpassed any in Earth's history.