The thing that surprised me most is that Luffy was reading newspaper.I don't think Oda was planning for Sabo at beginning but he did brilliantly tied up the beginning to present. Luffy resolve to be Pirate King wasn't something that he just decided to do because he was destined to do but Luffy worked on his resolve by building his strength and making promise to Ace and Sabo since Pirate King is having most freedom that Sabo wanted the most.