User blog comment:Keekian/The topic of Haki./@comment-34109241-20180111225711

It took the 3 best fighters on the crew 2 years to learn the "basics" of haki. And they also learned from powerful and experienced legends of the One Piece world. If Oda had all of the weaker crew members just magically learn haki on the fly, that would be an insult to not only the monster trio, but to their respective teachers as well. I really don't think Oda has any intention of having all of them learn haki, because it's not something that's for everyone, it's a warrior thing. For example Robin is an archealogist, if she wanted to learn it she would have done so from the revolutionaries. On the other hand  Usopp had his awakening because it's literally his goal to be a warrior of the sea, so it makes perfect sense. The others don't need it, t here are other ways to make the other Strawhats stronger, some of which we are already seeing...

Nami - has just been given a sentient thunder cloud, and while it's obviously not Big Mom level anymore, it has the potential to grow stronger alongside Nami. And it gives Nami the ability to fly as well. Imagine fighting Nami in the sky when she not only understands wind currents better than anyone but she can also wield fire, thunder, and wind powers. Nami's future potential from here on is actually quite ridiculous right now.

Brook - His soul powers are already showing themselves to be something that potentially replaces haki. He has the ability to attack soul entities which not even haki can touch. And every person does in fact have a soul, so I don't see what's stopping Brook from attacking people's soul directly instead of using haki. Combined with his speed, ice powers, and music powers, and I think Brook is going to be just fine without haki.

Chopper - Can always improve just by creating new points, and I think his interaction with the Minks will greatly assist in this. In particular I expect he and Carrot are going to train/fight together and improve each other's abilities. I see Chopper even combining points in the future, imagine a Kung Fu Monster Point! Or a Horn Monster Point that grows massive horns to use as weapons.

Franky - Franky is always building and creating new weapons and armor. He also told Luffy at the end of Zou that he was going to build new weapons to fight Kaido. For all we know Franky could have a whole new "Battle Franky" model when we next see him. He's also going to improve when the Strawhats eventually visit Vegapunk. Seastone armor in particular would be something of an endgame armor for Franky.

Carrot(Possible SH) - Seeing as they are a warrior nation, I'd find really it odd if Minks did not know haki, likely something "raw" and not fully understood with a different name, just like the people in Skypeia knew Observation haki. Pekoms was also shown attacking a logia. And to elaborate on what I said above about Chopper, I think either Rumble Balls will work for her too, or Chopper will create special ones for her to go Moon Lion even without a moon.