Hmm, Age of Wonders 3 finished off with 9 races, so I would admit to being pleasantly surprised if we got all the way up to 12 Factions(like the 12 races of old AoW1, or even 2's numbers of 12 then 15). Especially since it's more work designing a Faction(larger unit lineup, Faction-based tech tree) than it used to be to design a race, but one can always be optimistic!
Personally, I'm not expecting 12 different Factions, but rather the combination of Factions + Secret Techs to help composite different ideas. If nothing else, I could see 12 Secret Techs happening first. Partially since they would be easier to design, with a smaller tech tree, and fewer units, especially with more often having faction-independent units such as mechanical and creature allowing for easier design involvement. Also, though, because they represent conceptual niches, as distinct concepts of playing the existing Factions. Kind of the idea behind the fantasy trope of having many different kind of Elves(High/Dark/Wood/Gray/Sea/etc.)
If anything, I would also be more likely to expect enhancements by new game mechanics(Racial Governance styled one perhaps?), or simply expanding the existing tech trees(new unit mods and operations, new faction-unique structures or covert ops options, and doctrines, or even every unit having an upgrade tech, adding new abilities, better rank-ups, or even a fourth mod slot).
I'm getting sidetracked from the original topic, though, so moving these thoughts to the Brainstorming thread.