One PieceForming
Ussop will be killed by Imu in future sight
The big Ussop moment coming up in Elbaf will be him standing up to Imu to protect and motivate Luffy when he is defeated on the ground, similar to Enies Lobby. But this time he will be right in front of the villain, not at a safe distance. Ussop will then develop future sight, seeing his own death, but deciding not to back down and dying a brave warrior of the sea. But before he dies, it turns out that Luffy had the same vision of the future and managed to get up and drive Imu away with a final attack, similar to jet gatling.
Supporting thoughts:
Ussop has to get future sight if he wants to be the best sniper and to be able to defeat the Blackbeard dude that can teleport. Fitting upgrade for the final battle and would explain, why he got observation haki all the way back in Dressrose without it being relevant in the meantime (bc if he gets future sight right away against Imu that would be an asspull).
Ussop needs to fulfill his dream of "dying" a brave warrior. And it must happen in Elbaf because of course it does. But he also has to live to see his dad and to fight teleporter guy.
Luffy also has to get a big upgrade, so this is the best opportunity.
This is just subjective: I feel like the scene in Enies Lobby was something Oda copied from his idea for this upcoming scene, since he tends to take inspiration from his end of story plans for early arcs. This might be why he chose to have Ussop say (and Luffy repeat) "It is not like this is hell" or something. So this could be a nice setup for him to say this time: "This might be hell, but I do not care, you will beat him anyway".
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