Shanks’ true intention is to make Nika liberate the world.
Think about it. At the start of the story he traveled with the Nika devil fruit across the oceans stopping at every island he came across. It is know that devil fruits have a mind of their own, and he knew that, hence he was sailing a lot to give the fruit a lot of contenders to choose from.
After he saw Luffy ate it he, just like he puts it “bet my arm on the future”, and gave him his hat all to make Luffy more and more ambitious for his dream.
So now Shanks acts as some sort of a “guardian angle” for him and helping him escape situation he wouldn’t be able to otherwise. Prime example is saving him at Marineford and stopping Kaido beforehand. At Wano he made sure to let the World Goverment know that 2 Yonkos are looking after this island so Luffy won’t have to come back and save it if the World Government got plans for it. Also count all the stuff of plotting against Blackbeard behind the scenes.
Why do this? Like Roger he knew what the Void Century was (before departing with him before Laugh Tale). At Chapter 1116 it is clear that Roger left his crewmates with a message that is probably to let as many pirates on the sea. Hence Crocus guarding the entrance to the Grand Line and Rayleigh being to only way to get into the New World. So Shanks’ message was probably to help get the right pirate into the seas.
*by UnrealPotatoSlayer
