C3 was the most divisive story to say the least. And the ending also divided people. Even Mercer himself has stated that he doesn't think the Rite of Catatheosis was the best choice. As it may not hold Predathos back forever and now most of the Betrayer Gods are lose. Plus, without their master's command, the Devils of the 9 Hells will intesify their infighting in order to claim lordship over the 9 Hells. And Hell's Bells were not seen in positive lights by everyone in the end. In and out of universe.
So, I think C4 should address everything I've written here. C4 should be set centuries after C3. Everyone from every party in the past is dead. Perhaps technology has even advanced to the levels of the Eberron setting. But the Betrayer Gods and the Prime Gods either waged another war in the past, or are waging one at the current time. And many fear that this is a second calamity. Plus, with the advances of technology mirroring those in the Age of Arcanum, some fear another apocalypse is coming. Especially since it was the greed of mortals that lead to the Calamity.
Is history repeating itself? SHOULD it repeat itself? Or is there a way to avert it? Are the changes made between 3 and 4 bad or good? Or are they mixed bags? And what will happen if Predathos shows up again, unfooled? These should be the central themes of C4 in my opinion.
