Realistic. The world will be fine, not so much for most of the lifeforms that currently populate it. Earth has gone through evolutionary resets before. The existence of deep sea hydrothermal vents with methane loving organisms means that Earth will most likely NOT become like Venus, even when all feedback loops run their course. The carbon released and washed into the oceans will feed the species that produce oxygen, just as it has before.

Humans have become their own asteroid.