User blog comment:Salubri/New Characters and Reveals in the Future of Bleach/@comment-1432572-20100903130303

very interesting...

Anyway, we've seen that there are capable Shinigami out there that could take over as a captain. I know this because of the Shusuke Amagai filler. He was never heard of, but was introduced in a semi-clever way. Maybe that's how Kubo intends to introduce Captains. Or perhaps the other Noble Families will come into play, not sure how though.