If they price cut and sell Natal as a stand alone that would be a better option rather then just bundling all systems with Natal. It would hurt adoption rate but aren't they going to cost $80 individually? A $50 price cut across the board would be more appealing for most people and help them further second place with a $150 arcade. It's not $100 "WTF you don't own one?" price point but would be getting closer and closer :P
It's just that simple.