In my opinion I think Kishi is just dragging this story out and conclud Shippudden with a cliffhanger. He probably wants to drag it out to make up ideas for a third Naruto prequel. Why do you think Kishi bring Kaguya, history, godlike powers, and other dimensions? It's because and this is my only prediction. Naruto will end with a cliffhanger revolving around Madara's return. Plus we still have so much information we still have not found out, and not to mention ever new chapter brings in something new to the story. Shippudden will end but not the Naruto series entirely. Plus.... Why do you think Kishi has been saying he doesn't know how to kill Madara? Because.... He still has plans for that character.