Anyone for a good debate?

[Keeper of Dol Guldur]

What about the end?

I think that end may have come if Sauron had won control of Middle Earth. Then, after he had subjugated the rest of the peoples to Conquest, War, Famine or Pestilence, and finally they all fell, the only thing left to deal with his evil would have been the Valar, and they would have perceived his tremendous growth in power and ability as a threat to themselves and much more 'their concern', especially if one of Sauron's goals upon regaining that power was to free Morgoth from purgatory.

Of course, not that many evil dictators really care about paving the way for their former mentors to come back. "Yes, the world is mine! Now nobody will complain when I totally relinquish my throne to the very guy I replaced!" It just doesn't make sense. More likely Morgoth's Plan B entailed that upon failure, he could find a loophole if somebody like the ambitious young Sauron decided to attempt the same thing he once had.