I don't think that's the kind of slavery that WotC would be shy of, in particular if they made leading a revolt a big part of the plot.
I know you're against the idea, but I really, really think that "Season of Champions" is referring to Gladiators from Dark Sun. Whether that means they'll also make a push toward a PvP-style module, or some other way to bring out the word "Champion" to make it fit DS better than say, an AP-plot where you're lost in the Athasian Desert, or not, I couldn't say.
But I don't disagree that Dragonlance is a possibility, just not, IMO, as likely as DS. I don't think the placement of Soth in the Seasons mock-up is supposed to mean that he falls under the Champions banner.
I could be wrong, though!