Given The Winds of Winter has taken 12 years and isn't near completion, and Martin is 75, the books won't be finished by him. It did feel in A Dance With Dragons as if he had made it almost impossible to finish.
Robert Jordan's series was finished by Brandon Sanderson (from Jordan's drafts and notes), which was good inasmuch as the story got finished, but it was a noticeably different style. I don't know if Martin plans out his works ahead of time like that, they seem to be suitably tightly plotted that it's hopefully the case should the worst happen. I wonder if it's one of the areas where AI might be employed to mimic someone's style to finish their work?
O.
