Could Athas suffer any event like the Sundering in FR? This could mean a "planar rift", opening new zones to be explored, and allowed possible new elements to be added, for example the psionic ardents, or orders of monks.
It could, but what's the point?
The thing is that it is, well, I won't say impossible but at least very very difficult to recreate Dark Sun in a way Wizards would like. That's because there are multiple requirements that are mutually incompatible.
I've seen a lot of suggestions about removing slavery and other unsavory parts of Dark Sun from the setting. But to many of the setting's fans from way back, those things are an important part of what makes the setting tick. I mean, sure, tweak things a bit (e.g. figure out a way to remove the forced breeding part of the mul), but Athas is not supposed to be a nice place. Tyr having abolished slavery is part of what makes Tyr special, and a threat to the established order. Dark Sun needs to be a Luke Cage-type setting ("This place sucks, but I can change at least some things about it for the better"), not a Wakanda setting ("Everything is great, but we need to defend against outside forces that threaten us").
But on the other hand, slavery is sensitive stuff. I can totally understand why some folks see it as a way to cheapen what happened to their not-so-distant ancestors. And that makes a setting where slavery is a central component a potentially controversial product, even if the subject is treated with sensitivity. And Wizards doesn't exactly have a great track record with sensitive things, so there's a fairly big chance of them effing it up.
These two factors are mutually incompatible. It's like when I was getting my first glasses and wanted a particular pair of rims that I thought looked good. About a week after I ordered them, I was informed that I needed to select another pair of rims, because it was impossible to get the right shape for my prescription with those rims. So the only reasonable option is to not make Dark Sun at all.