The character of Shanks is shrouded in a lot of mystery, making it difficult to predict his actions. However, there have been numerous subtle clues that have led me to believe that he has a specific plan in mind. Shanks promised Buggy that they would reach Laugh Tale on their own ships, yet in the past 24 years, he has made no effort to obtain the Road Poneglyphs, except for the one he probably already has. This suggests that he has been waiting for something, or someone. The prophecy of the birth of two sovereigns, which was heard by Oden and Roger on Fishman Island, states that the two will have 25 years to meet. With only one year remaining in the world, Luffy has already met Shirahoshi, but his Devil Fruit powers have not yet fully awakened. The Gomu Gomu no Mi fruit was eaten by Luffy around the 9th year since the prophecy, one year before Shirahoshi's birth.
It seems that Shanks was attempting to create the next Joy Boy and knew the truth behind the Gomu Gomu no Mi and the Hito Hito no Mi, Model: Nika Devil Fruits. In fact, if you reread Chapter 1, it becomes clear that the fruit was not meant for Luffy to eat, but rather for Ace. Shanks was likely convinced that Luffy was the one destined for greatness after hearing the same words that Roger said, and so he inspired Luffy to set out to sea and gave him the trademark straw hat. The Roger Pirates' Journey: Despite it taking Roger's crew 14 years to reach Lodestar Island, Luffy has already made his way to the gates of Laugh Tale. Some might question the seemingly convenient progression of Luffy's voyages. Why did Oden have the last wish to open Wano's borders? Why did Rayleigh go out of his way to train Luffy? Why is Shanks pursuing the One Piece now? Why did Roger turn himself in to the Navy after returning from Laugh Tale? What was said between Roger and Shanks after their return from Laugh Tale? This leads us to a speculative conclusion: After reaching Laugh Tale, Roger learned the secrets of the world and realized that he wasn't Joy Boy, but 25 years too early. With his impending death, he made arrangements to ensure the appearance of Joy Boy in the next 25 years, indirectly helping the Straw Hats speedrun their journey. After returning from Laugh Tale, Roger laid out a plan for his crew to pave the way for the arrival of the next Joy Boy. He likely gave each of them specific tasks to fulfill: Shanks was tasked with finding the next Joy Boy, and possibly more. Oden was instructed to open Wano's borders to allow Joy Boy to reach Pluton. Rayleigh was to act as a gatekeeper in the New World, ensuring that Joy Boy was strong enough to move forward. Roger's role was to inspire the next Joy Boy, to encourage them to set out to sea, and to bring about a new era. In Chapter 1054, Shanks declared that it was time to claim the ONE PIECE, as the wait was over. Prior to making this announcement, Shanks was gazing at Luffy's bounty poster, which would have confirmed for him that Joy Boy had finally awakened.