There is a second option, the faction of the module "the Black Spine" could discover, explore, settle and conquer a second world next to Athas, and this could be a mixture of classic D&D standar and Dark Sun touch. They have founded a lot of slave colonies, and someones escape toward the "land within the wind" ( = Faywild), and they aren't wellcome by the eladrin(high elves). Then it would be like a strange twist of the isekai genre, from a D&D world to Dark Sun, with the cultural shock. Maybe that faction has also discovered the world of Jackandor, joining to the "party" between the two previous factions. (as we say in our land "we were few and the grandmother gave birth!" (= As if that weren't enough!).
Other idea is a totally new adventure, a sequel, or spin-off, of "the Black Spine", but this time not for PCs from Athas, but from Spelljammer or other space of D&D multiverse. Or the cult of Tharizdum, the elder elemental eye, creating secret hidden cells in Athas. What better place to hide? Then the psionic powers wouldn't be too necessary for the PCs because they aren't in a place where arcane magic can hurt the plants.
* If they are working in a new psionic handbook we should see UA about the psionic races: blues, dromites, synads, elans, maenads or the xephs. (It is curious, now I imagine xephs as cousins of giths and elves, maybe were giths who escaped to the Feywild, and the synads to the Shadowfell, and the synads would enjoy a special racial trait to create telepatic link with a "monster pet" or an ally, allowing a player to controll the synads and a second PC).
* Didn't Chris Perkins create a homebred world, Iomandra, with a lot of ideas from "Councyl of Wyrms"? But we would need playtesting and feedback of dragons as PCs. What if I wanted a pearl dragon as PC?
Councyl of Wyrms should be designed to allow enough space where we can add later all the dragon species, even updated version from previous editions, for example the cobra dragon, or the minidragon as monster ally from Dragon Magazine #146.