Board Thread:Questions and Answers/@comment-5775318-20130223175459/@comment-11051098-20140223153356

This is a question that still remains to be answered. I would guess that Kubo have thought of a solution for this, and I hope he reveals it sometimes.

As for the medallions, they're not a problem anymore. Every single Shinigami who has achieved Bankai received one of the Shin'eiyaku pills Urahara created, so even those who didn't get their Bankai stolen, are outside of the risk now.

As for Ichigo, he appears to not be included, but Fake Zangetsu was always the source of his Quincy powers, which is probably the reason why his old Bankai couldn't be stolen. And since Ichigo considers Fake Zangetsu to be a part of the real Zangetsu, I think his Bankai still can't be stolen.