The unannounced expansion, titled 'One World', was spotted by a fan posting on the official 2K forums. The database simply lists a "Expansion - One World Content", with no further details provided.
The last Civilization V expansion released was Gods & Kings, which introduced new civilizations, leaders, units and technologies, and featured the return of religion and espionage.
Neither 2K nor Firaxis - which went on to develop critically acclaimed strategy title XCOM: Enemy Unknown - has discussed additional updates.
A Civilization MMO is in development for release in Asian markets. The game is being created by a team of 100 people at South Korea-based XL Games.