... going to be huge
Even the EEDAR agrees, but at a long term:
“At this time, we do know that pre-orders are relatively strong, compared to other Wii products,” he told Edge. “By the end of the holidays, the Wii MotionPlus install base in North America and Europe should be well over three million. Of course, our forecast could be conservative... Yearly sales could balloon much higher.
“For the Wii MotionPlus, we currently expect the install base to reach over 11 million units by the end of Nintendo’s next fiscal year in March 2011, a 15 percent penetration.”
Honestly I didn't know that the pre-orders were strong for WSR, anyway quite big numbers for an add-on
http://www.edge-online.com/news/analyst-ten-million-motionplus-sales-in-2009