The Steam page for Sid Meier's Civilization V: Brave New World shows a playable demo was released yesterday on Steam for the turn-based strategy expansion (thanks Frans). There's no detail on the demo, so here's word on the game:

Sid Meier's Civilization® V: Brave New World is the second expansion pack for Civilization V - the critically acclaimed 2010 PC Game of the Year. This new expansion provides enhanced depth and replayability through the introduction of international trade and a focus on culture and diplomacy. Your influence around the world will be impacted by creating Great Works, choosing an ideology for your people and proposing global resolutions in the World Congress. As you move through the ages of history you will make critical decisions that will impact your relationship with other civilizations.

Sid Meier’s Civilization V: Brave New World also introduces nine new civilizations, eight new wonders, two new scenarios, four new gameplay systems and dozens of new units, buildings and improvements offering an expanded variety of ways to build the most powerful empire in the world.