The way Civ VII handles "Civ Unique" wonders makes Leader Specific Wonders more likely, I think: they aren't really Exclusive, you just get a substantial bonus to build them. That still makes it possible to, for instance, build the Baths of Hatshepsut if Septimus is busy with something else.
While I agree with this, hence while I am not ruling it out, I do think signs are pointing toward a "hard cap" on wonders available in the antiquity era (at least in default play modes). It's the best way to ensure the 7-wonders win-condition remains balanced with the other win-conditions, no matter how many antiquity civs are added to the game. So I'm thinking 8-ish "universal wonders" that appear in every game, plus the specific civ-associated wonders of the players on that map (1-5, maybe 8 (and if 8, might explain why Tonga's wonder was in the antiquity stream despite not yet being on the map)). Always 13-14ish wonders to compete for, no matter how big the full civ pool grows.
An antiquity leader with unique wonders would represent moderate risk to that balance. Possibly still doable depending on what other bonuses they get compared to other leaders. Although, even then I am dubious we
want a leader with a unique wonder taking up their design space, as it would mean that leader likely is
only good for playing in a specific era and otherwise useless, barring the idea of wonders that might plausibly be built in any era.
EDIT: One other thing I like about this idea, if true, is that it will just overall better utilize and differentiate wonders. It always felt weird to me how many "wonders" in past games just felt like they were "just sort of there" and were struggling to represent actual architectural feats in later periods. Wonders, the idea of architectural marvels, always felt like more of a thing associated more with age, especially antiquity. By making antiquity more "wonder"-oriented and associating civs with particular wonders, it is kind of encouraging a four-way breakdown of wonders:
1. Civ-associated "
cultural" wonders, which may reflect any one of these below categories, but are also just really good representations of that civ's culture, both contemporary and forwards/backwards in time.
2. Antiquity
universal wonders, which are largely
architectural marvels (since antiquity is our "building" phase). For now, these seem to also include "broad cultural ideas" like the Mausoleum of Theodoric, but I think the less one of our universals is an architectural marvel, the more likely it will be replaced in DLC as it is just a placeholder for a civ (like Mausoleum being replaced by Stonehenge).
3. Exploration
universal wonders (like, potentially, Notre Dame or what looks like it could be the Walls of Benin in our promo image), which are not necessarily architectural marvels so much as representations of massive feats of
religion and/or
trade (or whatever the "tech tree" equivalent to our religion mini-game will be).
4. Modern
universal wonders, which I could see representing marvels of
diplomacy or
technology (like a return of Amundsen-Scott Research Center or Biosphere).