The thought of a new super power in a shounen manga terrifies me. It's almost never a good thing. That too easily introduces the possibility of runaway power level escalation and unnecessary techniques (like with the sharingan, or Tetsusaiga in Inuyasha). Because Rokushiki can be explained as an application of haki, it should be explained as an application of haki. That does not mean it will, but doing so would avoid falling into among the worst of shounen cliches. Look at Hunter x Hunter and Fullmetal Alchemist as examples of shounen powers done right. The mechanics of nen and alchemy are explained in detail from the start. Both mangaka stayed true to their own world, allowing for easier suspension of disbelief. Nothing is worse in a fantasy story than being forced to question the mechanics of the world. It is already known that high ranking Marine have to know haki. If Rokushiki is a haki based form of martial arts, it would be a perfectly plausible explanation, resting squarely within the One Piece world we already know. If it is a completely new supernatural, unrelated to haki or devil fruit, it could potentially open One Piece up to the worst possible shounen cliches.
I understand that, but I think Oda is different about it; he's wise enough to avoid the dangers of the Shonen cliches. He has a solid plot as a solid background. I'm confident he will not sacrifice the plot in favour of a cliche that could go nowhere. At first sight, the current tourney seems to be not the best example of it. But, this tourney is much more complicated that Dragon Ball ones for instance. In DB, the first tourneys was about power and the fights and about who was the winner, etc... The last one was different, because there was a plot line outside of the tourney that was much more important than the tourney itself (Majin Buu entering the scene outside of the tourney). Dressrosa tourney advances in the same direction, but it goes beyond that; the plot in OP, namely, Law's plan, the Marine acting around the toureny and in all Dressrosa, CP0 and the government, all of it creates a much more complex plot than the one we had with Majin Buu in DB.
This chapter showed us, Oda is playing his game in a way that covers all the fronts. Coming back to the new techs topic, I would say, that if a new power or tech is introduced it will be in a way that it will serves the development of the main plot. If that is not possible then, or it won't be introduced at all or it will be but it will not take a central place in the arc. For sure, it wouldn't have an staring role comparable to the one Rokushiki had in W7. I image something like some few panels about it, with not much explanation of it, and move on with the central plot. In that way I would like it. I mean, its possible to do it avoiding the dangers of the chiches.
