Koala and Vegapank say it clearly, the war will be fought with ancient weapons and the one who will be in possession of them will be the one who will get his hands on the One piece and will be the king of the pirates, not surprisingly another thing that Teach aspires to (besides being King of the world), it is actually a means for him to then achieve his true goal of becoming king of the world and dethroning Imu, but he cannot succeed as Luffy will beat him before he gets the One piece, just as Luffy's dream requires the One Piece for Teach's it is equally necessary and he needs to get his hands on the treasure and ancestral weapons to then be able to really challenge Imu, but we know that it won't happen because Luffy will beat him first. Very easy. The final war like that of the second world anticipated by Vegapank is between Luffy and Imu so yes, those who think that Teach will succeed are actually wrong and do not understand that dethroning Imu is connected to getting your hands on the One piece and that is also why Dragon and Sabo are depicted in the double page with those who aspire to war for the One piece, they too now actually want it to be able to take part in the war against Imu.