I'm saying that over the next three or so (probably one or two) generations it could be completely done. Right now, put up signs stating the metric distances on them. Then start training students to use metric instead of the inches system (what's it really called, anyhow?), but still teach them our system so they at least know it. Eventually everyone who was stubborn enough to not adjust will die off anyhow, and about 50-60 years from now we'd be completely metric.