WHile I'd like to see Dark Sun reprinted and revised, I'm not banking on it anytime soon. (THough they are reprinting the Dark SUn novels, so, as the saying goes, "Never Say Never".)
However, there are some logisitical problems to overcome, needless to say.
One of the biggies is the "Defiler vs. Preserver" magic. How would this tie in to the revamped 4E magic system?
New races can always be shoehorned in, though how Warforged would fit in (given the harsh climate), and Dragonborn [given the status of Dragons on Athas] is somehting to consider.
Then, there's the Paizo update from "Dungeon" and "Dragon" magazines a few years ago; is that going to be thrown by the wayside? (I'd actually be OK with that, as I honestly wasn't a fan of those articles.)
The Cosmology. While recognizable to D+D fans, Athas really had it's own Cosmology, and was widely seperated from other Prime Material worlds. (IIRC, you couldn't even Spelljam to Athas!!)
The twist on the PC races.... Seems like 4E is trying for some uniformity