Coming September 2013.
* New Culture Mechanics including Great Writers and Great Musicians who create masterpieces to spread culture to distant civs (supposedly you can create the Mona Lisa or things of that nature.) New Culture Victory condition.
* New Diplomacy Mechanics including a World Congress which unlocks with the first civ that discovers all civs on the map. The World Congress meets to pass resolutions that affect many aspects of the game. Also, the diplomacy AI has supposedly received an overhaul.
* New Trade Mechanics including international trade routes which are set up through caravans or cargo ships, give gold and research bonuses, and allow easier spread of religion and culture. You will also be able to share food and production between cities internally.
* 9 New Civs. Poland is the only confirmed new civ. Assyria is likely due to the siege tower in the above screenshot. Portugal is a strong contender, especially with the new trade emphasis, and Zulu and/or Kongo are likely due to the new Africa scenario.
* 2 New Scenarios - American Civil War and Colonialism in Africa
* 8 New Wonders and new industrial age ideologies - could that mean corporations?