@SunWuKong:
so these are my 2 reasons:
1. all this haki stuff (which was confirmed as haki) started to take a role briefly after they reached the red line, the border to the NW…i think that is very foreshadowing...
I still kind of think Oda is kind of punning the word (and expectations) as much as foreshadowing, and it's not intended to be clear cut in any language… but, I'm going to leave this one be until haki gets more clearly explained. It might become a major point in the new world, but it's such a hax ability that we know so little about so far.
And I understand what you're saying, but regardless of who might or might not be able to use haki so far; from almost everything we've seen of the story so far, Logias have been and still are the top dogs. Admirals, Ace, and BB, regardless of mentioning haki and being a D., really didn't make his play until he found his perfect Logia. I don't doubt it will become relevant, but I seriously doubt it'll become relevant so Jinbei will become nakama or Luffy can pwn an irrelevant boss.
edit: if i remember correctly it is said, that every man ever entered amazon lily was killed, so how could roger learn haki from them? if you respond that the elite kuja pirates, who can travel on the ship taught them, why should they and did they than taught others who can use it also, too?
That's not really what I'm implying. It'd be more like Elder Nyon/Gloriosa, who left AL to chase her love or whatever. Hell, it could have been Gloriosa, but if it was Shakky it would go farther to explain Hancock's age/timeframes.
So like… the Kuja all seem to know the haki ability. Sexist maybe, but it makes sense the Kuja possibly mastered it as a hax ability to overpower the men that they fought.
Someone from AL (take your pick) met Roger along the line, and fell in love with Roger, or Rayleigh, or just felt like abandoning the Kuja, I don't know. Regardless, whatever she saw in Roger, she probably became the ultimate traitor in teaching him and/or his crew the haki hax, but did it anyway. Shakky makes sense, because... I doubt said person would really be mentioned again, or ever try to go back.
DISCLAIMER: It's just a theory. I don't have an answer for Sentomaru, but he has a female seiyu in the anime. Maybe she's just really butch? Or maybe an boy born on AL and cast out? I don't have an answer for Buggy either, but he seems to be the failure of the Oro Jackson crew. And, well, he's Buggy.