They defiantly don't deserve to die and none of the current kages came off as heartless or blood thirsty. And even a couple years ago in the series something like the joint shinobi army would have been impossible. The ironic thing is Obito/Madara/Black Zetsu and I guess even Pain to a degree could have assisted with world peace. Forcing everyone to work together has it's merits. To be 100% honest for a little while I seriously thought Obito or perhaps even Madaras real plan was not the Moons Eye plan. I thought that could have been made up to force everyone to work together. Because the Moons Eye plan sounded so dumb and Obito/Madara delayed using the ability for so long that I thought it maybe did not exist. But I felt that was perhaps to cleaver and anti-climatic for kishimoto.
Sasuke should know best that death just causes revenge. Killing the current kages will at best force the world to kill Sasuke. Which he apparently is now trying to do so yeah. It's now the world VS Sasuke. But everyone else is sort of in a bind right now. There are a few possible ways I can see the Ninja world being made into a better place. Honestly the way things are now there is already a strong bond between the Leaf,Sand and Cloud... Well that is if killer bee lives.
P.S
I just thought of something funny... After the final battle Sasuke is laying on the ground moments before death. He reaches up to grab Naruto and Sakura to say his final words. He says that everything hes done since leaving the village was not about his brother itachi or revenge for his clan. He just wanted Sakura to love him instead of Naruto.... then he passes away. (The End)