Media event set for September 9, launch likely ~10 days later.
Apple Discontinuing Messages Beta for Lion on December 14th
Dear [User],The email indicates that in order to continue to use Messages, users must upgrade to OS X Mountain Lion. OS X Mountain Lion is available for $19.99 on the Mac App Store [Direct Link].
The Messages Beta program for Lion will end on Friday, December 14, 2012. We hope you've enjoyed the opportunity to preview Messages.
If you'd like to continue using Messages, upgrade to OS X Mountain Lion from the Mac App Store. Messages is one of many great new apps and features built right into OS X Mountain Lion. Learn More.
Thank you for your participation in the Messages Beta program.
Messages is Apple's iMessage client for the Mac, and replaces iChat in OS X Mountain Lion. Apple had originally launched it as a beta program for existing Lion users while Mountain Lion was being completed.
It has been long known that Apple planned on discontinuing the Lion beta, but Apple is only now given customers a timetable. While Apple suggests that customers can upgrade to OS X Mountain Lion to continue using Messages, some customers' computers may be too old to support the latest OS X release.