Not offending anybody is probably more about not wanting EUIV to end up on the TV being lambasted as a 'slavery game' or something. That's bad publicity. That's why Paradox also refuses to cover the holocaust in HoI.
Paradox refuses to cover the Holocaust (and other aspects of the Nazi regime) because doing so would mean losing out on a huge market for their games in Europe. Not to mention a Holocaust decision/event chain would just be in extremely poor taste considering how recent it is (historically speaking).
However, I believe that Paradox will cover slavery in at least greater detail than VicII in EUIV. Slavery was a huge and quite profitable business/industry in the later years of the game, so leaving it out while adding so many other features and depth to the economic system would be ludicrous.
As for those who think covering slavery would draw the ire of the moral guardians, may I remind you that VicII allowed you to hold slaves as a governmental policy and yet no one threw a hissy fit on national television? To be perfectly frank, PDS games are too much of a niche market to appeal to the sensationalists that prey on big name titles like Mass Effect or Grand Theft Auto. Even if they did, what would they have to show for it? A trade screen with the word 'slaves' beside a slider? That's hardly the visceral and brutal depiction of slavery that would inflame passions in the media.
Now before we start getting off topic. I'll say what I want to see in EUIV:
- An improved combat system similar to what Paradox implemented for CK2. Just the right mix of hands-off and player interaction for a grand strategy game in my opinion.
- No more mono-culture/mono-religion provinces. A simple percentage would be adequate, no need to go into VicII levels of detail here.
- Greater detail on countries outside of Western Europe. I don't especially care about the native Americans or Indian minors, but please add more detail to Eastern Europe and the Middle East.
No more Comet Sighted events!
A thousand times this! Though I have a feeling the developers will be cheeky and add in an identical event with different fluff just to spite us