If Sauron prevailed...

[Galadriel55]

And some of us, even who check the Downs OCD-style, need time to work the grey cells and produce an intelligent-sounding answer.

As to what would happen immediately after Sauron's success, I haven't yet decided. But what occurred to me is Sauron won't be able to triumph forever. One of the themes that runs through Tolkien's works is that evil always undoes itself, sooner or later, one way or the other. In the long run, Sauron's actions will turn on him. He will weaken, or the resistance will strengthen, but either way there will be something that would spark his downfall (if imagination permits, you could even say that Saruman's ghost will come to haunt him and counteract all his plans ). And I think the Valar would exploit that moment - perhaps send another Istari mission, or communicate more directly in an Ulmo-talking-to-Tuor fashion. I suppose that brings me to say that I don't think the Valar would intervene in Middle-Earth until the time came, but neither would they turn their back on it. Later Age Valar take a minimally-interventional approach, and they will not launch a second War of Wrath, but I don't think they've gotten so huorny and inward-turned that they will not feel compassion for the fate of Middle -earth.

I agree with Inzil that evil will not be allowed to rule indefinitely and that Valar or Iluvatar would help, but I disagree that the demise would necessarily be at their hands. I would think that the overall trend through the Ages is for the great powers to take increasingly indirect approaches, and let Middle-earth inhabitants decide their fate (thus also making them take more responsibility for it). The other trend is that "fighting force with force" gradually becomes "evil will make its own undoing [which may be exploited smartly to increase that undoing]".

Rhun, I'm curious, did you have a theory already when posting the thread, or are you also torn between multiple scenarios?