In Dragon Ball, Goku was trained by Master Roshi, Kami and King Kai.
In Naruto, Naruto was trained by Kakashi and Jiraiya (maybe more).
In Rurouni Kenshin, Kenshin was trained by his master.
The list goes on.
Recently, we were informed by Oda that this current arc will be the last adventure of Luffy as a 17-year-old.
Kuma has sent strawhats to specific islands for their power-ups.
I can only speculate other members' intended power-ups but I believe Luffy was sent to Amazon Lily because of that island's famous Haki (maybe not extremely famous but if I remember correctly, Smoker mentioned/recalled it).
However, due to the war, Luffy fled the island without the power-ups to rescue Ace. So how will Luffy learn/master Haki like Kuma intended to or who will teach him?
I could see Hancock training him but Silvers Rayleigh could also do that.
What do you think?