The coffin will most likely be shown at the end. it depends what is shown in between the chapter; just like they did with Sasuke.
The main content about next week's chapter will surely be about the new battle encounter about what's going to happen. Perhaps, Naruto/Bee meetin' Madara's 6 Paths or Sasuke meting Itachi.
It might also be something unexpected like showing the Kakashi's battle, focusing on the Kages or who knows, Naruto expressing his love to Hinata finally...
I'm expecting many things but I don't think Kishi will give us a chapter where he reveal the 6th Coffin and goes on revealing Kabuto's plan. For me, the story and big Kabuto's moment should be when he confront his opponent.
I'll remain skeptical for now and give it a 7. Let's see how much I'm surprised.
