Or you fundamentally change the setting, which would make a lot of fans skip any products.
Whether that's true or not re: fans skipping if you change the setting, I think there's an open question as to how much of the potential audience would even really know/care, because how many of them even have played DS or care out the specifics re: chattel slavery vs. serfdom/indentured servitude?
Only 11% of D&D players are over 40. Only 15% are 35-39. You'd probably have to be either over 40 or pushing 40 to have played 2E Dark Sun at this point. And 4E Dark Sun definitely did not have many people play it, given it was a late product for a short-lived edition (I also have no idea how prominent slavery was in it - less prominent than 2E I dare guess).
So at most we're maybe talking 25% of the market even having played DS (and probably much lower). And how many have strong opinions on chattel slavery being vital to the setting? Half? A quarter? Less? How many equally see an actual psionicist class as vital to the setting? I'm going to guess that's a lot HIGHER than the number who demand chattel slavery.
If we can do DS without a dedicated psion/psionicist class (and it seems most people feel we can, even among grogs), we can do it without chattel slavery, because we're really talking about a very small percentage of the potential market. The majority of people buying Spelljammer will not have played Spelljammer, which was last cool in like, 1990. But they'll have heard it was cool. The same applies with Dark Sun. Things people who've never played get excited about in Dark Sun are Half-Giants, Thri-Kreen, Sorcerer Kings, Psionics, Brom's art, Desert Survival, Weird Materials for Stuff, Planetary Romance, No Gods. They're not "chattel slavery!". That's like, so far down the list.
So TLDR is it's not going to matter now. Yeah that might have been fatal if it was 3E and most people picking up DS were existing DS fans and so on, but now? Nah.