My hypothesis is that Imu either is Lily, or someone with a close connection to her, still alive since the Void Century because the Op-Op fruit’s immortality operation was used on them.
Which is that I think Caribou’s going to tell him where Pluton is, and then he’s going to knock down the Wano borders with his quake powers to get at it.
But the WG burned their bridge with Mihawk, so which is more likely: Mihawk teaming up with the WG for the final arc, or some big clusterfuck between the Four Emperors? :|a
1) Loses her casual invulnerability
2) Releases her Supreme Ruler Haki to affect the people around her