actually if danzo had killed sasuke hagormo would have given the sealing jutsu to naruto alone. he said he split the power this time to keep them both happy but he's capable of just giving it to one. without sasuke the war would be over and they could have moved on.
Then Obito would have won or Madara would have won, which would have lead to Kaguya. Either way, had Danzo killed Sasuke at the time using Shisui's Mangekyou, then the entire world would have vanished with him in the coming months. As without Sasuke, Naruto wouldn't have been able to stop Obito, Madara or Kaguya.