Board Thread:General Discussion/@comment-4957813-20131130185522/@comment-5216690-20140604192159

no, it was sealed. 1. a similar thing happened to ichigo, it was sealed and w was using the sealed state fighting. that's what happened to kenpachi also 2. In order to get the shikai for ichigo, he hap to face a life or death situation in order to finally hear the voice of zangetsu, again that's what happened to kenpachi. 3. the reason it is in constant release is because both of them have little to no control over their immense spiritual power, in order to fix this their shikai are always on. Note, however that this all happened after they have discovered the name of their zanpaktou.

In conclusion if they properly learn to control their spiritual power most likely it would go into a sealed state.