Hey, i have a little theory regarding what the final message on The Uchiha Tablet is.
Since it is required for a shinobi to have the Rinnegan in order to resurrect the Juubi, i believe the final message, only decipherable with the Rinnegan, is how to seal or fully control the Juubi.
I beleive that the SO6P new that eventually someone would acquire the Rinnegan in the future and that there was a good chance that person could turn out to be evil (this has been the case of all Rinnegan users other than the sage). Because of this he likely assumed that the new Rinnegan user would eventually try to resurrect the Juubi in order to gain ultimate power. The Sage being the great man that he is, aslo likely assumed that the Rinnegan user would not be able to fully control the Juubi as not even the Sage himself could, he was forced to seal it within himself. For this reason he was forced to inscribe a method of sealing or controlling the Juubi in hopes that once the new Rinnegan user acquired the eyes, he would read the Sages' inscription.
My theory is also supported by the multiple times Madara and Obito mention that the Juubi's power will be out of their control soon, yet they don't seem too worried about the most powerful being in existence running rampant. I think that this implies that Madara or Obito know either how to seal The Juubi, or a method to control it.
The only plausible method for them figuring out a way to seal or control The Juubi is through the final message on he Uchiha Tablet, only decipherable by the Rinnegan.
Since it is required for a shinobi to have the Rinnegan in order to resurrect the Juubi, i believe the final message, only decipherable with the Rinnegan, is how to seal or fully control the Juubi.
I beleive that the SO6P new that eventually someone would acquire the Rinnegan in the future and that there was a good chance that person could turn out to be evil (this has been the case of all Rinnegan users other than the sage). Because of this he likely assumed that the new Rinnegan user would eventually try to resurrect the Juubi in order to gain ultimate power. The Sage being the great man that he is, aslo likely assumed that the Rinnegan user would not be able to fully control the Juubi as not even the Sage himself could, he was forced to seal it within himself. For this reason he was forced to inscribe a method of sealing or controlling the Juubi in hopes that once the new Rinnegan user acquired the eyes, he would read the Sages' inscription.
My theory is also supported by the multiple times Madara and Obito mention that the Juubi's power will be out of their control soon, yet they don't seem too worried about the most powerful being in existence running rampant. I think that this implies that Madara or Obito know either how to seal The Juubi, or a method to control it.
The only plausible method for them figuring out a way to seal or control The Juubi is through the final message on he Uchiha Tablet, only decipherable by the Rinnegan.