Magic Mouse User Guide Suggests Mac OS X 10.6.2 Release in Near Future
To use your Apple Magic Mouse and its full range of features, update your Mac to Mac OS X version 10.5.8 or later and install the Wireless Mouse Software Update 1.0; or update to Mac OS X version 10.6.2 or later.
While OS X 10.6.2 is not required for the Magic Mouse to function, users running OS X 10.5.8 through OS X 10.6.1 will have to install a separate software update to enable support for the new device. The mention of OS X 10.6.2 suggests that Apple plans or at least did plan for the update to be released to consumers around the product launch.
Apple has seeded three builds of OS X 10.6.2 to developers, with the most recent having been delivered last Friday. The update notably addresses an issue with guest accounts that has resulted in some users losing all data from their regular user accounts.