In Tolkien's short lived "sequel" he had men becoming orc-like themselves. Not in looks but in evil. Even evil cults were being formed.

Plus, you have to refer to the second prophecy of Mandos. Mandos fortells the return of Morgoth.

Here's the passage Michael Martinez e-mailed me. It's a qoute from the History of Middle-earth volume 5. Here it is

(S)31 Thus spake Mandos in prophecy, when the Gods sat in
> judgement in Valinor, and the rumour of his words was whispered
> among all the Elves of the West. When the world is old and
> the Powers grow weary, then Morgoth, seeing that the guard
> sleepeth, shall come back through the Door of Night out of
> the Timeless Void; and he shall destroy the Sun and Moon. But
> Earendel shall descend upon him as a white and searing flame and
> drive him from the airs. Then shall the Last Battle be gathered
> on the fields of Valinor. In that day Tulkas shall strive with
> Morgoth, and on his right hand shall be Fionwe, and on his left
> Turin Turambar, son of Hurin, coming from the Halls of Mandos;
> and the black sword of Turin shall deal unto Morgoth his death
> and final end; and so shall the children of Hurin and all Men
> be avenged.
>
> "(S)32 Thereafter shall Earth be broken and re-made. and the
> Silmarils shall be recovered out of Air and Earth and Sea; for
> Earendel shall descend and surrender that flame which he hath
> had in keeping. Then Feanor shall take the Three Jewels and
> bear them to Yavanna Palurien; and she will break them and
> with their fire rekindle the Two Trees, and a great light shall
> come forth. And the Mountains of Valinor shall be levelled,
> so that the Light shall go out over all the world. In that
> light the Gods will grow young again, and the Elves awake and
> all their dead arise, and the purpose of Iluvatar be fulfilled
> concerning them. But of Men in that day the prophecy of Mandos
> doth not speak, and no Man it name, save Turin only, and to
> him a place is given among the sons of the Valar."

This is only a rough draft though. There are problems, Tolkien never really developed this.

Jon