@rubia_ryu:
I see where you're coming from, but I was sticking with the arcs themselves without the "prologue" arcs. Jaya was a lot longer to build up to Skypeia because of the obstacles the crew encountered, and it's not a good comparison to Sabaody v. 2, which was essentially, "meet up and set sail". In any case, the Skypeia arc was one of the longer ones in the entire story and Fishman Island is making its way up there too.
Actually, I can see that if Oda left in everything he planned for this arc, it would stretch even longer. The flashback could have been extended a lot, but driven readers out too impatient for the story progression. Even now, some readers are getting bored. It's about as long or longer, yet it's less action because the crew isn't in the middle of a war zone and are doing less exploration. I'm sure Oda is only saving that last point for later.
Ok, but i think it doesn't matter if an arc is longer than the others or not, the really important is the saga. Ok, fishman island will become a long arc, but the story is mostly concentrated there, meanwhile arcs like skypiea are the continuation of other arcs. In conclusion fishman island will be a long arc but a short saga, meanwhile skypiea is both a long arc and saga (ignoring water 7 saga and supernova saga or whatever oda called the saga from thriller barck to timeskip), so people shouldn't be panicking because of the lenght of the arc since everything is compilated in the arc itself.
Besides I see that this arc will have at least 25 more chapters until they left the island or whatever rest of it, and that without think on things like fishman karate dojo, jinbe's former crew,… because I don't know who Oda'll handle them. So the arc will have 65+ chapters more or less the same that skypiea, but having only 5 chapters of shabaody and probably 1-2 chapters, 3 at his most to reach the surface (only reach it, whatever happens there it's matter of the next saga) the fishman island saga will have 73+ chapters, meanwhile skypiea saga had 85-86 chapters. Of course the saga could lenghten in my eyes (with thing like hody flashaback, mini-jinbe brook's style fhlasback, and lots more of things speculated by me) but talking objectively at this point in the arc fishman island shouldn't be a long saga.
well, if it lenghtens, then I would classify it as a saga as long as skypiea saga.
Hmm, I think i've deviated in some point, so i'll rephrase my opinion in one line: Fishman island saga won't be one of the major sagas of One piece, in spite of the lenghty of fishamn island arc.