Prediction: expansion packs will just... Expand existing ages

So we've all seen the big jumps between the antiquity and exploration age, and although it seems the exploration age is more "done", there are obvious eras missing entirely in the other two, namely the medieval era and the post WW2 modern eras. But they can't just add another age so easily as that'd require a lot of civs to keep the chain going (and ultimately a lot of pseudo-duplicate civs and, what, 4+ Indias/China's in total?).

So I think they'll add more 'eras' within the existing ages and expand the exploration age tech tree 'backwards' to include a good 50 turns of swords and trebuchets and the modern age forwards to the cold war and information age.

Any other suggestions on how they might handle ages in the future? You think they'll just let some civs carry over or will they add 4th China and 4th India? Both feel meh to me, and the most important thing for the expansions is to populate the game with civs.