User blog comment:Kaido King of the Beasts/The Nature of the Zou Arc/@comment-972068-20151208090234/@comment-34981281-20151209235458

Who's to say that Zou or Wano are part of the same sage as Dressrosa? Personally, I feel like our usage of the term 'saga' no longer applies to Oda's storytelling. There's enough content in Dressrosa alone to split it between 3 or 4 arcs. The Collosseum was it's own contained story just the same as Whiskey Peak. It had it's own 'end boss', even. We didn't even meet Pica or Riku (unmasked) until it was over. The Birdcage itself could be an arc. The post-battle chapters could be an arc.

I think all One Piece fans need to be reminded from time to time that it's us, the wiki, who designated the start and end for each arc based on what agreed worked best. And for some reason, we picked grouping arcs by island instead of story. According to Oda, the arcs should be as follows. Oda's version starts Water Seven at Aokiji, which we list as part of Foxy's arc. That means what Oda counts as one arc, we count as three and a half. But are these Sagas? He seperated Impel Down and Marineford, though. According to Oda, actually, there are only two sagas: pre-timeskip and post-timeskip.
 * Episode 1 - 冒険の夜明け - The Dawn of Adventure - 1-95
 * Episode 2 - 偉大なる航路「グランド・ライン」への挑戦 - The Challenges of the Grand Line - 96 - 216
 * Episode 3 - 天空の黄金卿 - The Golden Lord of Heaven [Heavenly Sky] - 217 - 318
 * Episode 4 - 麦わらの一味対世界政府 - The Straw Hat Crew vs. The World Government - 319 - 441
 * Episode 5 - ゴースト島「アイランド」の冒険 - The Adventure on Ghost Island - 442 - 513
 * Episode 6 - 進入！ 大監獄！！ - Break In! The Great Prison!! - 514 - 549
 * Episode 7 - 史上最大の決戦 - The Great Decisive Battle [The War on the Summit/ The Paramount War] - 550 - 597

So really the official arc (or what we consider arcs) breaks could be anywhere. The official saga (or what we consider sagas) breaks could be anywhere. I don't expect Punk Hazard, Dressrosa, Zou, and Wano to connect or flow all that well.