It's probably Elbaph, one way or another. Imu REALLY wants to take over the place, to use it's people as their new army for something coming in the future. Plus, this way, Oda gets to at least show us Imu's "Yokai" form.
But, just for the sake of argument, where else could Imu go?
Well, the first place that came to mind was to fetch the Ancient Weapon Uranos, so that Imu could use it to "erase" Elbaph the same way that they erased Lulusia. If Imu can't have Elbaph, then no one can. Better to wipe it off the board. But, the problem with that is, I don't think Imu was onboard Uranos when it was used to destroy Lulusia last time. There's no reason for Imu to go onboard themselves, since it doesn't seem like Imu needs to be onboard Uranos to power it or to make it work or anything. So, chances are, it's not that.
Imu COULD go to Egghead Island, in order to get the Mother Flame for some reason. Either to power Uranos, or to power something else, even. But, again...I don't think there's any reason Imu would have to do that themselves.
Imu could go to fetch Vivi from Big News Morgans. But...that would be a bit of a non-sequitur, since it's not like we saw Imu got any news or intel or anything. It'd be a unexpected twist, but it'd come kind of out of nowhere. And, while it would raise the personal stakes quite a bit, it really doesn't seem like the most pressing matter in the world, right now.
The Moon is a interesting idea. But, that would also come out of nowhere. And there's been no sign that anyone was using the Moon or any of the technology up there before Enel brought it back online. So, I feel like if Imu wanted to go to the Moon, they'd have to fight Enel first. I feel like this is unlikely.
Could Imu go to Impel Down to free Doflamingo? Doflamingo did seem to know some secret about Imu's existence. And Doflamingo would possibly make for a stronger body than Gunko for Imu to "pilot". But, again, that feels like it would come out of nowhere. Even though, fans would likely lose their minds over "Devil Doflamingo".
As long as we're thinking outside box...what about Imu going to Zou? That'd be random, I'll admit that. But, the thought of Domi Reversi'd Zunesha is a interesting one. Plus, the Minks getting Reversi'd might make for a decent replacement army for Imu, if the Giants are no longer on the table. The Minks might be the second-best choice for Imu.
Imu could go out to battle whoever it was that attacked Mariejois. Whether that's Blackbeard or the Revolutionaries or both. But...we've gotten a few looks at Mariejois, recently. And the situation seems to be under control. Or, at the very least, the fires are all somewhere "over there", and haven't reached the main castle, yet. So, with the Gorosei and Shamrock seemingly dealing with the situation, it doesn't seem like Imu really needs to go in to back them up.
Imu going to Lodestar might be interesting. If only because that would give us the first glimpse we've ever gotten of the island. Plus, that might be the Strawhat's next stop, anyway. So, Imu might just be getting a head start. Random, yes. But, it'd be randomness with the purpose of setting things up for the next arc. Which I could see Oda doing. Lodestar might have some ancient technology that Imu wants to use.
Imu could go back down to where that Frozen Giant Strawhat is. Maybe Imu could activate something they have hidden down there? Or unleash some sort of "prisoner" that they have frozen alongside the Giant Strawhat? Another true Ancient Giant like Oars, maybe? I could see Imu sending someone else to deal with the problem on Elbaph, in their place. And Imu might have other servants we haven't seen yet. The God's Knights came out of nowhere, after all. But...that wouldn't really be "leaving" Mariejois, really. And we never saw Imu contact the Gorosei when they went down there, before. So, Imu's probably going farther away than that.
Imu going to Punk Hazard, possibly to take control of the Galleila Giants, might be interesting. We've seen with Imu's Giant Frozen Strawhat that Imu does have some connection to "freezers" of some kinds. And if Imu decides they can't get ALL the Giants in Elbaph...you might as well go for the Giants you already have. Since Punk Hazard is World Government property, still. Imu settling for "frozen leftovers" could be a interesting enough development.
Imu could be going somewhere deep underneath the sea. Somewhere that's been covered by the flooding waters. It could be Imu's the only person who can get down there, due to whatever their unique nature is, so Imu couldn't send anyone else to to this for them. For some piece of ancient technology or a weapon or something, perhaps.
So, Elbaph's still the most obvious choice. I could see Oda giving us some sort of twist, though. I'm having a hard time coming up with a slam dunk idea of where that could be, though. Where's someplace that would require Imu themselves to go, that they can't trust anyone else to do in their stead?
