This is just about enough of a theory that I thought it best to put it in the Theories board instead of the main board. Recently, I've been re-reading some of the manga, and was startled by the top left panel of this:

Tobi says the Sage of the Six Paths created a sealing jutsu that has been passed down, with which he sealed the Jyuubi.

Sounds simple enough, but could that have been the same seal that was used to seal the Kyuubi into Naruto? Here's my reasoning.

As we know, the Dead Demon seal allows its user to seal something either into oneself or into someone else, but the user must pay the price with his soul.

The Dead Demon seal responsible for creating Naruto's seal, after a little tweaking, became what the Kyuubi acknowledged was the Sage's sealing jutsu:

Could the Dead Demon seal be a rudimentary version of that original sealing jutsu? When performed by someone who isn't the sage, it maybe that the user's soul has to be eaten, but what it might mean to perform it while possessing the Rinnegan. Quite frankly, I'm not even convinced the Death God summoned by the jutsu is even a living being. It seems to me to be more of an alternate dimension, one where, as its users claim, the sealed and the sealer will battle for all eternity. The Sage could have turned this dimension into the means by which he harnessed the Jyuubi's endless power.

If the Death God is actually the opening to a dimension, a number of possibilities open up. A new Rinnegan user (likely Naruto or Sasuke, I suppose) could open that dimension without dying, allowing for such things as:
-the restoration of the Kyuubi's power
-the freeing of the previous Hokages
-some badass battles involving the above

It just wouldn't make sense to have the Death God eat them up, but never poop them out, AMIRITE??

This is, by no means, a complete theory, and my pressing need to go to the bathroom prevents me from adding more right now, but it's something I'd like all your great minds to discuss.