So how many unrevealed bankai (munus Hisagi's) do we have left?
Shinji's, Love's, Ukitake's, Aizen's, Yoruichi's, Isshin's, Ginrei's (Byakuya's grandpa), the rest of Zero Division (hell, they don't even have shikai revealed LOL), Zaraki and Unohana's still need explanation what they really do. So 13 (basically a whole new Gotei 13 LOL) in total. Also there are still those original, first-generation Gotei 13 captains (5 of which are of course Yamaji, Unohana, Ichibei, Nimaiya and Kirinji so at most 8 others left).
Kubo can still milk with more novels I guess. And then there is West Branch in the one-shot Burn The Witch hahaha