I am under the impression Oda strongly emphasized on cutting the story down to bare necessities in his most recent letter and the 5 year comment and the fast ending of the arc and everything... The man really wants to come to a conclusion with the story. And he'll commit even more to a sleek storytelling after the chaos this arc was, I am sure.
But how tf is he gonna do that when we have:
Dragon (still waiting), Sabo, Ivankov and the Rev commanders
Marines
Imu and the Gorosei at minimum
Blackbeard and his crew get fleshed out
Mihawk, Weevil among the former warlords lacking focus
Red Hair Pirates
Ancient Weapons (Uranus still missing)
Elbaf
Last missing Road Poneglyph
Laughtale
Straw hats/new emperors themselves will again have their own share of panel eating time whenever they fight
At minimum those things I mentioned, who knows what else I forgot, unless the next arc ties multiple islands and reveals the laughtale or last road poneglyph location or some shit.