By the way this spoilers also tells that Roger never planed on Shanks' becoming the pirate king/finding one piece, so the Shanks' inherited Roger's will theory(from the hat) was proven false.
He wanted his son to be that, and Whitebeard wanted the same. Ace had so much potential, but i guess Oda wanted for Luffy to inherit that will. Whitebeard even said so in his final moments