Very big possibility that The third kazekage has something to do with akatsuki. Maybe the founder of the akatsuki.

Now, who of you thought that Gaara would still be alive when they've fully extracted Shukaku? You think Zero would go like: Ok, thanks Gaara for your Bijuu. That's all we needed from you, you can go along now. We'll see you around in the sand village. Have a nice day?...