Ok first off. U guys are way off . Where do u see fire based.? It said the water vanished cuz of his reiatsu and to cool down the sword. Which meant it was too powerful. And where did it say he is in shikai form. That is just how it is. One is zamgetsu. The small one is zamgetsu and e big one is his shinigami/hollow power.
His shikai form gonna be that hollow form, he turned into when he fought ulquiorra or the form he fought Aizen in. This is a guess. And his banzai gonna be new. And no is not fire based. For now let's assume is w.e it is based.
Oh and I think ichigo banzai gonna be powerful than Yamato easily. Because it reiatsu made a river dry up. Yamato makes river dries up when his sword is in banking form. Ichigo blade was in normal form and the river dried up.
