Well, this decidely low-tech multiplayer option will be included in the next patch for Civilization V.
According to the 2K Games in the official forums:
The time has come to reveal the “much-requested addition” that I teased you all with in the most recent patch notes.
Hotseat is coming in the next big patch, which is currently slated for a June or possibly early July release.
For those of you that do not know, Hotseat is a method of playing multiplayer where multiple players take turns on the same computer. When one player’s turn is over, they get up and let the other player sit down to play their turn. We’ve received many requests for the ETA for this mode being added to the game and so I’m very happy to get to bring this to you guys today.
Also, this patch will contain far more than just Hotseat. The other details of the patch will be revealed in the future, but I wanted to get you guys this big news as soon as I could!
The feature was also included in Civilization IV. The chief reaction has been how happy the gamers are to play with their non-gamer wives, and the second reaction is: how about play-by-email?