The 4th age?

Well with the prophecy of Dagor Dagorath I would think that the 4th, 5th and 6th ages would have some role in the final chapters of the history of Middle Earth.

Tolkien in a letter dated 1958: "I imagine the gap [between the Fall of Barad-dûr and modern times] to be about 6000 years; that is we are now at the end of the Fifth Age, if the Ages were of about the same length as S[econd] A[ge] and T[hird] A[ge]. But they have, I think, quickened; and I imagine we are actually at the end of the Sixth Age, or in the Seventh."

I would speculate that something of historical merit could have happened at the end of the 5th or 6th age, as to what I could only guess!

But it would be a fanciful thought to imagine a final battle between Manwe and Melkor heralding the unmaking of Ea.

~ Narsil