I reckon that the spirit of the setting is being preserved, and the minor details can be fiddled with all they like.
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Hey, retcon cosmology, shoehorn in tieflings, make whatever changes are necessary
I would argue that these aren't necessary and that they aren't just minor details, but do indeed interfere big time with the spirit of the setting.
That's the big divide that's going to happen over Dark Sun, and why I think it's going to be such a glorious train wreck. Fans like, say, Purple up there, are old fans of Dark Sun. They don't want tieflings or a retconned cosmology.
On the other hand of the spectrum, you have people who haven't really played Dark Sun and don't really care. They go "Man whatever, just give the funky creatures!"
I think it comes down to this: What do you put more emphasis in? The 4e part, or the Dark Sun part?