Man this arc is pretty important… I dont care what people say it was time to know where luffy came from and how he is who he is. We know all about the other strawhats and their past but we only know how luffy acts we never knew what made him be the way he is. In my opinion it was perfect placement. I'm also a strong believer in the return of sabo. Why would Oda spend so much time building up Sabo's character (away from luffy and ace) when it doesnt relate to luffy. Oda doesnt develop characters and then kill them off. Mark my words Sabo is alive and with dragon. Dragon and Sabo both talked about freedom. It's just like oda to bring sabo back with dragon.
Ace wants to be loved
Luffy wants to be the best ever with his friends
Sabo just wants to be a free man from this goverment he hates
Ace found family with whitebeard
Luffy is on the road to pirate king with his crew
So sabo is defiantly with dragon.
I mean come on... Dragon in the same place as Sabo while he realizes he hates the world government. So expect to see sabo in the future.