After the knee jerk reactions have subsided, smokers will adapt or move on. I doubt NCL or HAL will be "safe havens" for long. For every smoker that moves on there are several non-smokers and even flexible smokers who could replace. The ships will still sail full.
On Celebrity, the casinos are non-smoking and on Princess there are smoke free casino nights. It could happen on Carnival.
The handwriting has been on the wall for sometime. Nobody should be surprised.