There were 5 previous version of Civ. For me, that means you need to have been in at least 3 versions (aka more than half) to be a "Series Regular" that
must be included in Civ 6.
If you ignore for a moment the conglomerations for "Vikings/Denmark/Norway" + "Celtic/Scottish" + "Sioux/Iroquois/Native American/Shoshone/Cree".
That leaves these
Series Regulars (by my definition) missing from Civ 6:
- Babylon: 5 for 5 appearances (Civ 1-5)
- Carthage: 4 out of 5 times (Civ 2-5)
- Byzantine: 3 times (Civ 3-5)
- Inca: 3 times (Civ 3-5)
- Maya: 3 times (Civ 3-5)
- Ottoman: 3 times (Civ 3-5)
- Portugal: 3 times (Civ 3-5)
The only two Civs that have appeared twice (and are not in Civ 6) are Austria (Civ 3 and 5) and Ethiopia (Civ 4 and 5). And although many would disagree, I do not consider either of these "Series Regulars". Again, personal opinion, but if these 2 do not show up in Civ 6, I won't care at all. How many people were up in arms that they left Sumeria (who appeared in both Civ 3 and 4) out of Civ 5? (I mean that as a real inquiry, not just a rhetorical question.)
Not that I want this, but Firaxis could do those 7 Regulars, plus one more alternate leader, and one brand new Civ (likely from Western Africa, Ashanti Empire perhaps?) all in one final Expansion and call it a day. There would be a lot of wailing and gnashing of teeth, but at the end of the day I would guess that most of us wouldn't pinpoint a specific flaw in this lineup. Sure it is poor from a TSL/geographic representation stand point. Yes, it lacks originality and unique flare. Certainly some very deserving Civs would be left out. But comparably, at least to me, if they did just one final expansion and left out one of those 7, I think the complaints would be a considerably louder (and well justified).
Getting back to the point. I hope that they do more content than just the 1 more "expected" expansion. It could be a 3rd expansion pack. I actually still feel that DLC on-top of an Expansion pack for a game like Civ isn't a bad plan. Honestly how many people play Civ 5 Vanilla vs. Gods & Kings vs Brave New World? I would argue, as I have in other threads, that the people who are buying the DLC are going to also have these expansion packs. Remember, we are in that odd in-between state between Vanilla and final content. We are playing the equivalent of Gods & Kings.