Honestly, I’ve always felt the “end the world” wasn’t literal, and more of a thing like “the way the world operates will change completely”. I think it’s probably going to be like Wano where Momo becomes shogun after Kaido is defeated.
So Luffy would take down the likes of Imu, Blackbeard, Akainu, the SHs would defeat the other admirals, and all the replacements of the admirals, the Gorosei, and Imu would do something like end the privileges of The Celestial Dragons, and result in the WG having a new military and government structure in place. And then we get some wise sage/Whitebeard type talk about how the world is ending because of regime change and I’m assuming property damage, and Pirate King Luffy summarily wrecking the shit of Imu, with all his friends taking out pretty much the entirety of the villain roster, bringing about The Dawn Of The World while Luffy parties like he does at the end of every arc.