Yamamoto, shunsui and ukitake are still captains?
And there was no real proof yet that isshin was ever a captain. There's one slight hint that he may possibly have been in one of the noble families, but aside from being a soul reaper literally nothing is known. And the line about captains maintaining the size of their swords would really be common knowledge to all soul reapers, so I don't think that really counts as a hint that he was a captain.
I'm picking minor points though, I have no intention of joining the debate for real >_>