Not surprised. The Wii will always be like the ugly dude who stands against the wall during school dances bobbing his head to himself. The Wii will always be relegated to that dance room wall, while the 360 and PS3 get all of the action.
The DS is getting a game, because it's a different market--the handheld market. Microprose (or whoever has the rights to the Civ series now) isn't willing to risk the game flopping, which is probably a very smart move for them.
This is just a pattern of what's to come, get used to it. With every multiplatform game, the Wii's version will be shoved to the back and just be ported from the PS2 version, if it ever comes out at all.
Oh well. This was probably among my most anticipated games, but I'm not surprised and I don't care as I'm used to this by now. Aren't you guys?