The clones are lying.
And the Black Zetsu is still alive (And so i think that the white one too).
You seriously don't think he died like that? What if Kishimoto wants us to think that he's dead for 50-100 chapters, and then suddenly appear and do something crazy?
Also there's still that white plasma that Tobi ordered Zetsu to put on Kabuto. You think it will be forgotten? Maybe he can recover himself from it?
What was in Bleach? We were supposed to think that Tsukishima got killed by Byakuya for few chapters, but he still was alive after this.