It wasn't Ichigo who asked for his Bankai. It was Renji when Urahara made him train with ChadI sure hope since this is the last run for Bleach that Kisuke's bankai will be released. And since this is the last run the bad guy has to be a major badass right? When Ichigo requested Kisuke to call out bankai during training he replied that it was not suitable......WTF?! What major disaster will be suitable!!!Thats my question for you all. What would it take for Kisuke to release his bankai? I wanna know!!
Anyways, just because he said it's unsuitable doesn't mean it's something disastrous. Chad's training required brute power, something Renji could supply. Urahara saying that his Bankai was unsuitable for Chad's training likely means it's a Kido-based Bankai. Makes sense considering his Shikai has so many Kido abilities
She never released it. We only saw it on her waist during a flashback of her and Urahara. Probably again during the Turning Back the Pendulum chapters