User blog comment:Kaido King of the Beasts/Chapter 813: Up in Vinsmoke/@comment-5398287-20160121132556/@comment-2125188-20160121145728

Sorry to break it to you guys, but this arc is much more than just transitionary. Jack WILL return to Zou (that will result in a major battle), and there are still reasons why we need at least some of the crew to remain on Zou. And trust me when I say the samurai stuff is just waiting around the corner just waiting to surprise us, and i'm sure at least some of the crew will still be on Zou when that happens. If Jack returns to Zou, Luffy may need to call in his grand fleet to help deal with him. The crew will almost certainly split up again. This is how I think they will be split:

Save Sanji group: Luffy (for obvious reasons), Nami (for navigational purposes and screentime), Brook (info about the Vinsmoke family and/or screentime), Franky (to repair any damage that Big Mom may have caused, ship maintainance and overall just for a little power balance)

Protect Zou group: Zoro (will need someone strong and reliable to protect zou), Chopper (to continue to tend to injured Minks), Robin (will definitely be a poneglyph there, even if there isn't she will explore to look for one), Usopp (just power and screen time balance. who knows, the minks might also become his followers as other races such as tontattas and giants kinda have).

Speaking of change from the usual formula, it looks as though we may have 2 concurrent arcs. Given both of these situations seem as though they're going to be long and feature major battles, I don't think having one of them as a flashback later on would work (however it is Oda, so he could pull it off, but it would just seem so weird given the mysteries and the scale of what's happening).