If anyone does make a mod which adds eras, it would be really cool, could double the length of the game
I've been thinking about what the future eras should be like, and here are my thoughts:
Future era 1:
Continues roughly in the same way as the modern era, with lots of new units and pollution creating improvements.
Future era 2 (awakening):
Adds new "Green" type of government (maybe 2: socialist green democracy and capitalist green democracy) , which would, if possible, slow population growth down a lot, but would improve efficiency (and therefore more commerce and/or industry) and add new pollution reducing improvements which would eventually cut down pollution to zero. After the pollution reducing improvements are built, civs would be able to go back to other governements.
During this age, no significant unit advancements would be made, but some older improved units should become available with no more natural resource requirements.
Future era 3 (exploration): This era should be filled up with small and large wonders which give massive culture boosts (space based).
Future era 4 (stagnation): With the neighbouring stars and the solar system colonized, what are the people on Earth to do? Reignite old hatreds of course. This age should add more military units, and have very few cultural wonders/imrpovements.