We've gotten word from a previously reliable source that Apple is discontinuing the Magic Mouse in favor of the Magic Trackpad. Our retail source has informed us that Magic Mouse inventory is not being replenished for Apple stores, and that Apple is finally phasing out the Magic Mouse.
OS X Lion has heavily focused on gestures, so to take full advantage of those gestures a trackpad is necessary, which is why Apple could be wanting to phase out the Magic Mouse.
A recent report has indicated that Apple could also merge iOS and Mac OS X into one operating system as early as 2012. With Mac OS X becoming more gesture based and Apple phasing out the Magic Mouse, iOS and OS X could eventually merge into one operating system
CultofMac is now reporting that the Magic Mouse has reappeared with a different product number.