I think it all comes down what people are looking for when it comes to Dark Sun. What is the core element that needs preserving (no pun intended)? Right now, Dark Sun seems to be several things people want:
- Post-apocalyptic meets pulp dying world where hope and resources are in short supply. Vance meets Howard by way of Burroughs.
- A D&D hardmode where PCs might be super-munckiny (24 strengths! Free Wild talents!) but still die quickly from dehydration, inferior weapons and armor, and monsters that make the Tomb of Horrors look like a Disney dark ride. Bring extra character sheets.
- An "anti-D&D" s setting where everything is flipped on its head. Cannibal halflings! Bards that poison you rather than spell cast! Psionics instead of magic! No orcs, no goblins, and dragons are psionic-magical God-Kings! There is not one word of lore in D&D that is true about Dark Sun, no assumption can be made, and nothing, and I mean nothing, is like it is described in the PHB.
- Fidelity to the original vision of the setting, without additions or subtractions, with or without the metaplot advancements. Nothing that wasn't in the original setting back in the 90's.
- A collection of new options (Races, subclasses, psionics) and rules (advanced survival, defiling) that can be ported to other games or used in homebrews.
Whichever you think is most important colors the rest of your choices on what to adapt. For example, the first point is the most important than the Barbarian class is a natural fit; tough armorless primal warriors seem a shoo-in for the setting. Yet If the second is the most important, barbarians are a no-go because they allow PCs to have excellent ACs easily, and having a good AC is a privilege for those cunning enough to survive low levels with bone armor and stone weapons. Similarly, if fidelity is most important, there is no way you can possibly accept sorcerers, warlocks, tieflings, or any other element that came post 2e as part of the setting since it ruins the very notion of DS's relation to magic and the planes, but if you want more options, then you want warlocks to get new Pact options, not banned altogether!
WotC will have to decide IF they are doing this, which parts are the most important and in what measure. If they want the setting beats and options but don't care about it being hard or keeping true to the setting, you get a 4e-ish style book that is mostly refluff, reflavor, and some new options to go with it. If they want to satisfy the original purist who want Dark Sun to be D&D are its most brutal and strange, they are either going to have to create a book that doesn't use 50% or more of the current options in the core, let alone doesn't generate leads to supplemental books OR they are going to have to re-write the game to accommodate all the changes. You MIGHT be able to get away with "paladins are unknown, check with your DM" but there is no way you are pulling off "In Dark Sun, you cannot be a barbarian, bard, monk, sorcerer, paladin, or warlock. Additionally, you cannot be an eldritch knight, arcane trickster, beastmaster, have any cleric domain but life, light, and nature, or specialize in any school of wizard magic except preserver or defiler."
So again, what is the most important parts you want to emphasize? What trade-offs are you willing to make?
I agree. Everybody has a personal and skewed view of what Dark Sun is (well, like any other matter) and that's what drives his opinion.
That's why no setting update to new rules will ever satisfy everybody.
Me, personally, I'd like to stick more to the feeling than the rule (of course based on my feeling.
I'm not against incorporating things that were invented after the first publishing, if they fit well with the basic idea of the setting.
For example, like many others I concur that mechanically and temathically speaking Warlock pact magic fits better with what a Templar is in the lore. And I would accept the inclusion of a reptile PC race like dragonborns or lizardfolk, if correctly implemented. Even tiefling, as a stretch, could be refluffed as "mutants" of some sort, without any demonic/diabolic association (the lore itself states that mutations are relatively common among humans).
What I didn't like was the tendency of shoehorning everything from the core books into the setting that was done in the 3e and 4e conversions. Dark sun is not Eberron or the Forgotten Realms, where "there's a place for everything". Quite the opposite. It was intended to be wildy different from the expected "regularQ game right from the start.