We are already past that point. The world is not reducing carbon emissions fast enough. I don't see how nuclear allows us to reduce them any faster. The bottleneck is funding and will of the everyday man.

The world won't become uninhabitable - global warming alone is not going to cook us. What will happen is more natural disasters, difficulty with natural resources and farming, and wars for those resources.

Climate engineering is the best hope to reduce global warming. Aerosols sprayed into the atmosphere, that sort of thing.