Shanks or Dragon will arrive after Hybrid Loki is defeated. One of them will be the one to drive out Imu, whose time and condition at sea level are limited. You’re being silly if you think Imu will be completely defeated right now.
There will also be a revelation regarding Biblo, as Chopper is heading over to talk to him now. He will likely reveal his own identity, the nature of Chopper’s powers, and how they can save Shuri from Imu’s control.
However, given the narrative hints surrounding this event, it is possible that Imu will completely compromise Yggdrasil. The giants, much like the Fish-Men and Minks in the series finale, will have to relocate to a new land (maybe redline?).
All of this will happen over the next 20 chapters, and there will be breaks because Zoro and Sanji have their own fights to handle, and each dedicated fight takes at least two chapters. Luffy won't return to fight, but rather to leave a promise for Imu, something that will be unsettling. That’s classic Oda.
Therefore, this elbaph arch will extend until the middle of the first quarter of next year.