User blog comment:Fintin/Haki/@comment-2117107-20100618003839

So far in the series, in the present time, Luffy has not had any help with training in any way... He gains in strength by himself, so why would it start now? While Haki is seen as a very powerful ability, as seen from the Dark King's use of it in the Human Auction House, I doubt Luffy will be trained to use it, as he will probably just gain experience from using it in certain situations.

Nevertheless, I doubt anyone will train Luffy, and even if someone does, it will be a while before then.