nintendo has little to do with updates in that game the developers do & they can add modes & maybe maps
can nintendo update like ps3 can with new maps zombies game info?
New maps very likely aren't coming due to the wii's memory restrictions..and DLC maps have never been done on the console before. I doubt a third party will be the first one to open that possibility.
Modern warfare: reflex likely won't be changing at all for as long as it's out.
Either way, DLC costs money. Bug-fixing patches and minor features (like killcam) MIGHT come along, being that World at War suddenly gained new game modes out of the blue while it was out, but don't count on it.