Several Dark Sun monsters are set to appear in Dungeons & Dragons upcoming reboot of its Spelljammer campaign, which is raising questions about the status of that classic campaign setting. Last month, Wizards of the Coast announced they were publishing a three-book boxed set titled Spelljammer: Adventures in Space, which will serve to reboot the classic campaign setting for the first time in nearly 30 years. However, recent previews of the setting indicate that it could also incorporate aspects from a different setting – the popular post-apocalyptic themed Dark Sun setting.
Last month, Wizards of the Coast released its first Monstrous Compendium, a free online supplement containing ten monsters tied to Spelljammer. The Monstrous Compendium contained a mix of classic and brand new monsters, including the Nightmare Beast, a monster that originated in Athas, the world featured in Dark Sun. A recent preview of Spelljammer-themed miniatures set to be released by WizKids later this year indicated that Spelljammer: Adventures in Space will feature the Braxat and the Ssurran, two monstrous races that also originally appeared in the Dark Sun campaign setting.
One of the core concepts of Spelljammer is that players can travel between different worlds using magic-powered ships, which theoretically means that a player can travel from Oerth (the location of the Greyhawk campaign setting) to Toril (home of the Forgotten Realms). So, it's certainly possible that players can travel to Athas using a Spelljamming helm. However, the presence of so many Dark Sun monsters suggest that Spelljammer will feature Athas in some way.
Originally released in 1991 (after the release of Spelljammer), Dark Sun featured a dark post-apocalyptic world featuring unique rulesets and takes on D&D fantasy. Wizards of the Coast revisited Dark Sun as part of its D&D Fourth Edition line of products, but the setting hasn't been mentioned much at all in any D&D 5th Edition products. However, Dungeons & Dragons did bring back several psionic subclasses in the 2020 release Tasha's Guide to Everything, which were a key component of Dark Sun's core ruleset.
Last year, D&D design studio head Ray Winninger noted that a classic campaign setting would make a "cameo" appearance in 2022. Based on what we've seen from Spelljammer so far, it looks like Dark Sun could get at least a fleeting mention later this year. Whether that means that we'll see a fuller Dark Sun release in 2023 remains to be seen, but Wizards of the Coast did note that another classic campaign setting was under development for a new product release.