He did say one. The only question whether one is the pinnacle of his power or the base. And yes, Matsumoto doing something useful and using a bankai would be quite interesting! But we all know that won't happen because Kubo doesn't do interesting. He does breasts! Big, bouncy, useless breasts!!!
Quick note: Did you notice when Bazz-B used his finger burner thingy, he said "1" ? what is that? the level of intensity? the number of fingers used? imagine if he used all 5. You know what Im kind of hoping for? that is if Matsumoto didnt get hit as well... that she ends up fighting alone while Toshiro recovers or something and she uses bankai or something.