User blog comment:Xilinoc/Ch. 553 - Frozen Cross/@comment-11003280-20131019070415/@comment-6916556-20131020170655

It is common knowledge that shikai regenerate over time. If Byakuya wills it, and has time to feed his reiatsu into his zanpakuto, it will regenerate. His bankai should return if he touched the shin'eiyaku. I imagine Kubo will wait for a As Nodt rematch before the bankai returns though. It would be pretty anti climactic if all off screen captains just go and rematch the sternritter with their bankai already returned to them.