Humanity may well have been exterminated if not for the Borg threat, definitely. Keeping humanity around was almost like keeping a pit bull, in the Dominion's minds: needed because an even stronger enemy was out there, but could turn on them with even the slightest "owner" mistreatment, hence the need for what they thought would keep humanity just peaceful enough.
But now, without the Dominion, the Confederation (which as you might expect, encompasses areas both formerly of the Federation AND of the Cardassian Union--and adds yet another layer of complication to the Graft issue) has to hope the war with 8472 keeps going and that neither combatant turns on them next.
About the industrial complexes...the Maricopa Research Center--and many other places like it throughout the Dominion's human-colonized holdings--was a place I see as very much like the place where the Manhattan Project was. I had actually debated using White Sands, too, or maybe even Trinity, but it seemed like that would yank people right out of the story.
Even if humans hadn't had access to industrial facilities...I still suspect rebellion would have eventually come, just as it did for the Cardassians in the prime universe--and that arrogance would eventually end up being the Dominion's downfall.
I really am not sure about the fate of humanity (Cardassiohumanity?) after this story. I just think there's no way it would be a cut-and-dried answer.