The next major Civilization V patch will add a hotseat multiplayer option that will let multiple players take their turns on one PC. Community manager 2K Greg has posted on the 2K forums with news of the patch, which is set to arrive "June or possibly early July."
We can probably expect more bug fixes and balance changes from the next update, too. "This patch will contain far more than just Hotseat," writes Greg, "the other details of the patch will be revealed in the future." For more on Civ 5, check out the official Civilization site.