Apple emailed users of the Messages beta on OS X Lion tonight that the beta program will end on December 14th.

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 included with the purchase of OS X Mountain Lion from the Mac App Store. With Mountain Lion, Messages replaces OS X’s former iChat application and integrates the OS with Apple’s iMessage messaging service.