Has anyone stopped to consider just how a wireless nunchuck attachment would work? The PS3 as I recall can connect with up to 7 bluetooth enabled assessories. If we have a motion controller and wireless nunchuck each take up one of those slots than we can only have a maximum combination of 3 remote/nunchuck players playing any game at once with one slot left over for an additional DualShock 3/Motion Controller/Wireless Headset.
It would probably be much more cost effective for Sony to simply attach the two with a cable the way that Nintendo does and the lower price could drive more sales of the assessory as well.