@skr:
Back in Impel Down, I believe Blackbeard offhandedly mentioned after he was punched that Luffy's haki had gotten stronger, which leads me to think that it is in every attack to some degree even without the blackening. I am slowly growing fond of the arm blackening thing. At first it put me off a little bit, but I wondered how else a new ability could be shown. A power aura like DBZ would seem out of place, gear 2 already causes steam, flushing, as well as heat waves, and leaving the attacks looking normal would be a bit confusing and unacceptable. So I was pretty happy with Luffy showing the versatility of his new moves and the fact that he doesn't need to be in dire straits to use them. (no apparent draw backs so far like gear 3 and the shrinkage.)
I rly like that new look of his CoA attacks, but i rly hope that we now wont get any new transformations(how his body changes\looks like) during he attacks. Iam wondering if CoC will be used by him so that we see a physical transformation but i doubt that. So far we have enough body transformations for Luffy, so that it should be enough to use them\combine them for the rest of the series. I mean we had like the first 25 volumnes only Luffy strechting himself in different ways and we loved it. After that he turned in his strechted arm during Skypia(okay, not rly a transformation but close to it) what i thought was rly cool and i somehow hope we may get that back combined with some CoA. Then we had gear2 and gear3 which also still have new potential combined with haki. So now having Luffy use again a few volumnes his new techniques and then thinking it
s necessary to see a gear4 or something else which transforms his body again is pointless in my eyes.
To sum it up, he should use more his transformations he had so far and make them even stronger\combine them in creative ways, instead of developing now every second arc a new fighting transformation.