With the Infinite tsukoyoumi casted, spiral zetsu can finally join Madara and black zetsu against the only threat left against them, Team 7 and probably the edo hokages. The only thing left for black and spiral zetsu to do is to fuse, both using Obito's body as host. With their powers combined and with Obito's eyes they will be a slightly weaker version of Edo Madara (Madara+Hashirama2.0).