I was just thinking after reading some other threads I don't think it would happen but I think that they can still be brought back via Edo tensei. If you think about the conditions needed to bring someone back with this jutsu then technically Kabuto still holds those conditions. You need their dna and their soul's must be in the pure world or whatever its called BUT also you need sacrifices when the 3rd Hokage sealed them in the death god it wasn't Hashirama's or Tobirama's souls that got sealed. It was the sacrifices souls that got sealed so if I'm right then all conditions are still met what do you guys think.