Devar Eliyahu: The verse teaches that a man does not have these two hopes, whether he gets weak or dies. He will die - where is he?!

Malbim: A man does not have these two hopes, whether he is cut when he is a Gever (in his youth, in his strength), not via weakness of old age, rather, via another means. He is weakened via death and will not sprout to live again. He is unlike a healthy tree that was cut - it does not weaken. A man who dies amidst weakness in his old age, where is he? Nothing remains of him.