Juubi's 3rd Transformation!!
In this im going to explain why the Juubi's last transformation already occurred.
This manga page
According to Kurama, not only is the Ten-Tails the source of all chakra, but is also the progenitor of everything that exists in this world. Kurama stated that it was a god that created countries and had the power to swallow oceans, split the land, and carry mountains.
Now pay attention to the part where it says that has the power to swallow oceans, split the land, and carry mountains, this will become important later on.
While in this page Kurama says that it is the energy that is around the world, which is just saying that he is full of Natural energy
While in this manga page the Juubi flys up in the air and a huge storm appears
Ok now to the theory!!!!
I think the Juubi is in fact the storm.
When it says that he can swallow the oceans (much like a hurricane)
When it says that he can split the land (earth quake)
He has not yet moved mountains so im blank on this one.
and him having nature energy, which a storm is nature energy, so it all makes sense
The Juubi is in fact a storm that wreaked havoc on the world.
The nature energy is the storm.