Someone has to sacrifice themself to make the 10 tails perfect.

My vote is Jugo, he will sacrifice himself so Sasuke or Orochimaru can take full control of the jubi.

I can't remember which chapter but Obito says that the only way for Madara to become the ten tails junchiriki (I'm sure that's spelled wrong) is for someone who is actually alive to do it.

Spoiler:

Some one would have to bring Madara back to life via rinne tensei. Nagato was originally supposed to do it, but used it on the leaf villagers and died. Since Obito now posses the rinnegan he would have to sacrifice his life to bring Mads back so he could become the ten tails jinchuriki (which kinda sucks for Obito when you think about it-- it's a double edge sword, he wouldn't even be able to even see this dream reality  he's been working to hard to achieve since he'd have to die to make it happen. So much for seeing Rin again in this perfect dream reality =/)

Juugo seems to be loyal to only Sasuke. I don't think he'd do something for Orochimaru right now. I seriously doubt that Sasuke has any interest in becoming a jinchuuriki. I don't even think Orochimaru would want to do that--unless it would tie into his ability to have the abilities of the Sage of Six Paths (which I do actually think Orochimaru probably wants).

I don't think the Juubi becoming "perfect" is the same thing as being able to use the Juubi's powers in whatever manner the person wants though. I think the purpose of becoming the Juubi's jinchuuriki is for being able to control its power better. I think the Juubi will reach its most powerful form on its own. I think Obito is probably waiting for that moment.

Could be wrong though as there's so many things that need to be answered concerning the Juubi.

Yamasaki Akaiko wrote:Juugo seems to be loyal to only Sasuke. I don't think he'd do something for Orochimaru right now. I seriously doubt that Sasuke has any interest in becoming a jinchuuriki. I don't even think Orochimaru would want to do that--unless it would tie into his ability to have the abilities of the Sage of Six Paths (which I do actually think Orochimaru probably wants).

I don't think the Juubi becoming "perfect" is the same thing as being able to use the Juubi's powers in whatever manner the person wants though. I think the purpose of becoming the Juubi's jinchuuriki is for being able to control its power better. I think the Juubi will reach its most powerful form on its own. I think Obito is probably waiting for that moment.

Could be wrong though as there's so many things that need to be answered concerning the Juubi.

 I just see it as a creature that is too powerful to not use in the story and I don't think Obito/Madara is going to achieve its perfect form.
The only way for the ten tails to become complete "perfect" is for all the tailed beasts to combine with the ten tails and the only way for that to happen is if someone becomes the 10 tails jinchuriki. I think Madara/Obito will be thwarted by the alliance so who else has world domination plans? Orochimaru and you guys already know about my "Sasuke isn't good theory".


Taken from Narupedia. 
"The Ten-Tails (十尾, Jūbi) is the primordial entity tied to the legend of the Sage of the Six Paths. Its chakra was divided into the nine tailed beasts and its bodysealed into what would become known as the moon, by the Sage in his final moments of life. The Ten-Tails is considered to be the creator of the world, and the herald to its end should it ever be revived.^[2] Obito Uchiha's ultimate ambition, which was created and designed by Madara Uchiha,^[3] the Eye of the Moon Plan, is to capture and merge all nine of the tailed beasts' chakra back into the Ten-Tails' body, and become its jinchūriki and then cast the reflection of his Sharingan on the moon, casting a genjutsu known as the Infinite Tsukuyomi which will put the entire world under his control."

Well if you're really interested in the Juubi and possible sacrifices, I highly recommend reading Sir Derp Obito's second part to his 1st theory.

http://narutobase.net/forums/showthread.php?t=372819

If you go to post number 65 and decipher it the best you can, it's a really eye opening idea about religion and how it could be tied into the Juubi.