Personally, I think I would find Lan's death and Nynaeve's corresponding grief certainly most heart-wrenching, while I'm not that sure about Cadsuane's possible death (and it seems a bit less likely that BS would find it that heart-wrenching, since he doesn't like Cadsuane that much).

Lan is of course in grave danger at the moment, since he is basically on a suicide mission to stop the Shadow's hordes from entering the Westlands. As said, there is of course lots of foreshadowing for Lan's death, e.g. in NS the notable sentence: "The air of Kandor held the sharpness of new spring when Lan returned to the lands where he had always known he would die."

But we will see.