Luffy's final fight is not against Blackbeard or Imu

Luffy's final fight isn't Blackbeard or Imu. It is difficult to know exactly how One Piece will end, but there are a few Chekhov's guns that Oda has set up that still need to be addressed by the end of the story. These set ups are why I believe that Luffy's final battle will take place on Laugh Tale and will be against Shanks. From chapter 1, Oda set up that Luffy's goal is to surpass Shanks as a pirate and build a better crew. Shanks then gives Luffy the straw hat and tells Luffy to give the hat back to him when he becomes a great pirate. Suppose the story of One Piece plays out exactly as everyone believes it will: with the defeat of both Imu and Blackbeard to save the world from their tyranny. We will also see a Void Century flashback which will add context to the history of the world, Joyboy, the Poneglyphs, etc... which will set up the reveal of the One Piece as Luffy and crew make their way to Laugh Tale. At this point, I believe we are set up to have three crews arrive at Laugh Tale: The Straw Hats, the Red-haired pirates, and Cross Guild (Since Buggy is always failing upwards and naturally will make it to the final island). With those three factions at play battling it out for the One Piece, it sets up both a Zoro vs Mihawk final fight so Zoro can finally become the world's strongest swordsman worthy of the Pirate King's crew (just in time for Luffy to become the pirate king) and allows Luffy and Shanks to battle to see who is the superior pirate. A fight where the winner gets the One Piece and the loser gets the straw hat. Of course, Luffy wins, returns the hat to Shanks, then claims the One Piece for himself to accomplish his dream of being the King of the Pirates.