PrimeSense most notably worked with Microsoft to create the first motion-detecting Kinect controller for the Xbox 360. If the report is true, then take the deal as a sign that Apple is looking into new types of user interfaces for future products.
One thing that came to mind is the upcoming Leap controller that will work with Mac computers. It's a motion sensor that sits beneath your monitor and can detect your hand movements, letting you virtually interact with games and objects. If the PrimeSense deal does happen, something like Leap would be a logical step for future Macs.
There's also the video game angle. There's been a lot of speculation that Apple would like to open up Apple TV to let you play iPhone and iPad games on it. A motion sensor in future Apple TV hardware would add to that experience.
Calcalist has a decent track record when it comes to acquisition rumors, so this report is very interesting.