Interesting observation regarding the IPs: every new civ except for Britain and Iceland is already an IP in the base launch game: Carthage/Tonga/Assyria/Silla in antiquity, Bulgaria/Pirates/Ottomans/Vietnamese in exploration, and Maori/Nepal/Qajar in modern. Note that there will still be a "Vietnam" IP in modern era (we started with two Vietnam IPs), which then opens up the possibility that Ottomans and Silla could feasibly occupy different eras (which is further supported by similar predicaments created by the placement of Sweden and Slavs in exploration).
I've also noticed that we have a lot of IPs hanging out in "clusters" around civs, as if to provide "realistic" IPs to interact with. However there are a few interesting "clusters" that haven't really had a "payoff" with an "anchor civ" yet (obviously Britain and Iceland indicate that not every new civ needs to come from a "promoted" IP):
Antiquity:
* Scythia/Sogdia/Huns/Xiongnu/Sintashta/Kushan/Saka - There are just too many of these, and that's not even including the outright Iranian or Indian IPs. I think we are getting an antiquity steppe civ sooner than later, and if I had to guess, Scythia is more likely than the Huns or Xiongnu. Although the modern Bukhara IP makes me wonder if Sogdia stands a chance. (personally, I think Scythia and the Huns would be excellent candidates as kurgan cultures to try out a sort of "clone/echo" design, reusing some assets/units but differentiating the civs mechanically).
* Cham/Yue/Taruma/Kavalan - I think based on these we are generally expecting a "maritime" SEA antiquity civ, as well as a better start for Vietnam, so I think the density of civs in this area suggest Cham's chances are pretty good as covering most of the bases.
* Caral/Chimu/Tiwanaku - Surprisingly dense here, I think odds of antiquity Tiwanaku are pretty solid. It also would serve as a very good starting point for any Chilean/Argentinian exploration era civs like Mapuche.
* Hohokam/Pueblo - Why do we have both of these in base game? Most of the IPs seem to be clustered around existing civs, but these aren't near anyone, one would have sufficed. I'm suspicious.
Exploration:
* Mexica/Mixtec/Zapotec - very comfortably setting up an Aztec civ. Still also hoping for Purepecha, would be nice.
* Zimbabwe/Shona/Kilwa (with Merina modern) - I think an exploration Swahili Coast civ is very likely. Unsure yet it it will be Swahili/Kilwa or Zimbabwe/Shona, but I think the former is just better connective tissue for the region. I don't think Swahili/Kilwa precludes the ultimate addition of Shona/Mutapa/Zimbabwe/Zulu/Boers or however South Africa is represented.
* Ava/Ayutthaya/Lan Na/Lan Xang/Pagan - Ignoring the clearer neighbors for Majapahit (Srivijaya, Sulu, Tondo), I still think this is a lot of adjacent IPs even for just a Dai Viet civ. I think the chances of Burma/Pagan are pretty solid.
* Just noting here also that exploration Japan is represented by Kamakura.
Modern:
* Oman/Merina/Zanzibar again, ignoring Buganda neighbors (Ethiopia, Luba, Nde), there's still a lot of these. I could see Oman or Madagascar happening. Maybe both.
* Nde/Comanche - same deal as the Hohokam/Pueblo, I'm curious if they have something planned for that region, although I guess these could be the modern "Mexico neighbors."
* Ifugao/(Sulu/Tondo + Rizal) - The attention being paid to the Philippine region makes modern Philippines seem an inevitability.
* Iceh/Bali/Burma - Although we do see other "broken up" civs in other eras (Persia, Aztecs, Inca, Russia) this...feels like a lot. I could see these accompanying a modern Indonesia or Brunei.
Potential Chains:
* Iceland into Inuit (also a nice modern complement to the Maori)
* Tiwanaku into Mapuche into Guarani
* Muisca into (Gran) Colombia
* Hungary into Austria