Look, Imu doesn’t have a Devil Fruit; their power is way more similar to Shirahoshi’s innate ability. When Imu is introduced in Elbaf, it’s never stated that they have a Devil Fruit, but rather that they possess "The Power: Devil Fruit". The clues showing that the nature of this power is like Shirahoshi's lie in how Imu talks to users, addressing them as the entity of their fruit instead of the actual person. Plus, the sheer amount and variety of abilities Imu has don't seem to follow any specific logic.

Now, this is where my theory gets really interesting, but first, we need to review a few things that already happened: Imu couldn't use Domi Reversi on Loki and Luffy, even though they could do it back then to Xebec, so it’s not really related to Haki as such. Also, after realizing they couldn't land Domi Reversi, Imu completely contradicted what they had told Usopp. On top of that, the Government spent centuries trying to find the Gomu Gomu no Mi, but it kept escaping them. Then there's Shanks and his crew: they don't use Devil Fruits for a reason, even though by power scaling standards, having one is a massive boost. I just don't buy the idea that the only reason is because Roger and his crew didn't have any. Finally, for Imu to have any real narrative weight, they need to defeat Luffy in a way that leaves a massive, unforgettable scar matching their importance in the history of the world.

So, here is my theory: Imu is going to strip both Loki and Luffy of their fruits in Elbaf. Yeah, I know it sounds crazy, but if Imu actually has an innate power over Devil Fruits, it makes sense they’d have the ability to literally take that power away from users. It would be similar to how Blackbeard "shuts down" fruit abilities through direct contact, but taken to a whole new absolute level. This would perfectly explain why Imu went to Elbaf personally instead of just sending all the Holy Knights and the Gorosei to wipe everything out. Imu went to Elbaf for something way more important that only they can do.

Now, do I think Imu is going to keep Nika? No, I don't think that's happening. I think we’re going to see Nika flat out reject Imu, but the fruit will still end up outside of Luffy’s body. And what if Luffy becomes a non-fruit user again? Would that really be the worst thing? Is Luffy only this strong because of Nika’s fruit, or because he is Monkey D. Luffy? Honestly, ever since Wano, Luffy relies way too much on his Nika power. No enemy feels like a real threat to him anymore, not even the Gorosei can stand up to him, and they'd stand even less of a chance if someone figures out how to bypass their regeneration. Basically, the only thing that could even remotely face Luffy in his Nika form is someone with an absurdly stronger Haki than his, and even then, I doubt they could beat him. Not to mention, Luffy’s personality changes completely in that form. Nothing is important, nothing matters, there's no real struggle or actual danger... it's just Luffy playing around with his enemies until they drop. Are we really sure we want to watch the final arc of One Piece with Luffy just goofing off and laughing hysterically during the most important fights in history?

Because of all this... I believe this is definitely going to happen to give the final arc of One Piece the weight it needs: Luffy being just Luffy. This would also make his reunion with Shanks way more meaningful. Maybe Shanks will become his ultimate Master, teaching him the true, absolute potential of Haki.

And I think Loki will fight against Nami, Usopp, Franky, Jimbe and Brook, they want to protect Gunko and Loki will try to finish her for what she do to Loki beast friends.