Originally Posted by Hassun

I have to say though, in the anime he clearly says it's released permanently (if the subtitles are accurate of course). His high spiritual power appears to have forced the sword to release (shikai) and because there's so much of it seeping off him at any given time he is unable to seal it back. He says this in episode 38 of the anime.

That would also explain the unique appearance of the sword (it doesn't look like the standard katana the lower ranked shinigami use.)

So in the end, I say his sword is released permanently, just like Ichigo's Zangetsu.