I'm starting to think that he has leaned soooo much with only using thunder and lightning shit because, and may Carrot fans forgive me, the fucking bunny with electric powers maybe had a shot at joining at some point (!!!!!) but then Oda dropped it and decided that Nami would have to go all the way in. And what happened with Zeus just ties the knot, by being the ultimate lightning powerup, because I can't honestly see how she will improve or get another powerup after this.
"B-but Brook has ice powers and Yamato does as well so you mean that Yamato isn't joining?"
I'm willing to bet that when Yamato joins, Brook's next showing will focus more on the Soul King stuff than in the chills of the Underworld so as to keep it even.
That's also why Zoro will never use the fire slicing he stole from Kin'emon to the full extent (Kin'emon can create fire as well), and if he uses it, Oda will make it sure to the readers that Sanji's blue fire from Ifrit can't be cut or some shit.
