Civ for DS would be PERFECT and we just might get it!
There was an interview with Sid Meier where he praised the DS as a possible platform for strategic games, because of the touchscreen and all that...
IIRC he also mentioned how a direct port wouldn't be such a great idea, but how a modified DS-specific game engine should be developed.
He explicitly said that no such game is in the works right now, but they're seriously considerig one, and should probably do it soon...
So probably, some kind of Civ, Col or A Centauri spin-off will eventually emerge on DS.
After all, Nintendo already has a great strategy franchise (Advance Wars DS is the latest) and Age of Empires for DS should be out in february... DS really is a fantastic platform for strategy games, it's pitty that Nintendo was held back with that "kiddy image" among casual gamers.