Kishimoto Sensei is a great story teller, and Truth to Tell, We can only try to anticipate him.
I must say that I love what you said about Kurama being a Force of Nature, That is perhaps why he and his siblings, the other Bijuu, cannot die. I also like your take, and that of others on the Sage-Kyuubi Mode Theory.
The One thing that I sense, and hope I am right, is this. Unlike Humans who attempts Sage Mode and Turn into Stone Either because they can't ballance it well, or they are doing it while moving, I think that: It is Impossible for a Chakra Being (and a force of Nature?) like Kurama to turn into stone.
Hence, If the Natural energy is being fed to Kurama, He'll eat and keep eating, and just grow stronger (and larger), without the risk of turning into a frog or into stone. This is the bedrock of my theory, and I hope that Naruto will use this idea, if at the end of the Manga, Naruto has tofight against the GM statue, or a re-assembled Juubi.
That would be the Bomb!