Yes, I'm wondering the same thing. It sure would be nice to have better interactivity with the EA Sports Active. We occasionally struggle to get some of the workouts to respond to our movements. I'd certainly spend $20 to improve it, if I knew it would help.
No, MotionPlus will not help with EA Sports Active. Only software specifically designed to make use of MotionPlus will use the device. You will be able to play the game while WM+ is plugged in but the device will not be utilized.