Not every plot thread will conventionally pay off as foreshadowed. Subversion of Caribou's storyline is possible. It stamps the world with a realistic sense when it occurs. Caribou is just a regular pirate that went from island to island carrying a ticking time bomb. It's a possible outcome, but fans wouldn't expect it because "It's a story and this is what normally happens". It doesn't have to pay off when he's currently involved, even though conventional storytelling would do just that.
I've always believe Caribou's Shirahoshi intel will cause the "Major Incident" that will involve the Strawhat Grand fleet

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