There is no need for him to die. I rather have them kill all the 5 kages or some other fodder characters. Despite, Guy probably surviving after Naruto giving him some life force. The fact is he is "Ninja" Wise dead. Kishi is smart in this sense. There is no "Springtime of Youth" anymore. There is no 500 push ups or pull ups. There is no walking around the village only using his arms. No more. Now he is confined to a bed or a walking stick. Guy is not a character i would have killed, after this he should probably be an inspirational speaker or teacher in the village teaching kids unable to use Ninjutsu. In summary, Guy still has a purpose instead of killing off the character unlike many more others Kishi can kill off.