I think that in some of the Black Ring writings or dialogue, a reference is made to the Black Ring occupying Yuthul Gor, the homeland of the orcs, and using them as slave labour.
Since the elves who lived in the Dark Forest are mostly or completely gone, it might also explain why there aren't any dwarves around either - they sealed themselves up underground when the forces of the Black Ring marched on the Dark Forest.
Still, more references would be welcome, especially if it meant seeing those races again (as more than 100% hostile monsters).
