Well it is a possibility. But I know Dark Seducers are in service to many different Daedric Princes. The ones who serve Sheogorath are called the Mazken. The Golden Saints are in the service of Sheogorath primarily. And seeing as how the events of the Shivering Isles kind of made Sheo disappear and the CoC was the new mad god who knows how it is gonna work out? Id say both have a 50/50 chance of being in. Hopefully all the Daedra are in though. I thought it didn't make sense that they were not available for conjuration in Oblivion.
Golden Saints can be seen outside his realm in Morrowind, and I think the Daedra Seducer from Daggerfall is the same think as the Dark Seducer despite their extremely different designs.
Golden Saints were even summonable.
I'm going to take a stab in the dark here and say that the changes we saw between Daggerfall/Battlespire Seducers, and Shivering Isle Seducers happened mainly because of all the shakeups that happened to Bethesda in the late 90's. Remember folks, that many of the key players left after Daggerfall, and the guy running the mad show, Julian LeFay, left after Battlespire was released, and subsequently bombed. Sure there's few hold outs left from the old days, Todd Howard being the most prominent example, but the creative team and direction is different then when it was back in 98. Despite Battlespire laying most of the foundation for the various daedra underlings we now know.
You can always hope for the Golden Saints and the Dark Seducers to make a return in another ES game but I don't see it happening in skyrim. :mellow:
That really all depends on whether or not the mad god makes a return, if he does, I don't see why the Aureal wouldn't show up in this game, there to fascinating a species to pass up.