The only part of Wano that I've reread was Oden's adventure, but just an estimation off memory, I think this war is already going to be 70-80 chapters long given how much was set up. Not sure if there'll be room for an extensive Ulti and PO backstory, but hopefully they get a chapter akin to Baby 5 or Seneor Pink's pasts. Their character interactions and personalities are really interesting, it'd be a shame if we don't see a glimpse of their childhood.