In Civ4 it was possible to play simultaneous turns or taking turns in any game, SP or MP. Simultaneous turns in SP is farily pointless though, and taking turns in MP is fairly unpopular except for pitboss games etc.
I have to say, since I don't know anyone with a DS, I'm disappointed there will be no hotseat play. I can't see CivRev being worth it just for the single player game.