Whatever happens - nuclear war or not - is simply not going to happen the way JWs think it will.
The UN isn't going to be crying out "peace and security". The world's religions are not going to be destroyed; if anything they'll be strengthened. Jesus and his horse riding angels is not going to be coming to save JWs from extinction. The Witnesses will be going on throughout the rest of their miserable lives in expectation of things that will never happen.