|The Lion version of Messages, which existed as a beta only and gave users a taste of the way the program operates on Mountain Lion, will never emerge from beta and will be discontinued on December 14, according to an email from Apple to existing Messages beta users. The change does not affect those running Messages on Mountain Lion, but closes the only non-ML portal to the service. Users are encouraged to upgrade to Mountain Lion, but those who can't will be able to continue to use iChat, which offered many of the same features but lacked the full level of message integration.
"The Messages Beta program for Lion will end on Friday, December 14, 2012. We hope you’ve enjoyed the opportunity to preview Messages," the email reads. "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. Thank you for your participation in the Messages Beta program." The email includes a link to the Mountain Lion page on Apple's website, which showcases its many new features over Lion.
No explanation for why Apple chose not to continue to support Messages in Lion was given, though the beta was pulled from Apple's website in June. Many Lion users have surmised that the decision is part of a continuing push by the company to get as much of the userbase on to Mountain Lion as can be moved there. This suggests that the company considers Mountain Lion a "reference release" that sets the stage for the next major version of OS X. Users who must remain in Lion for whatever reason can revert back to iChat at any time, but will lose the ability to send SMS-like iMessages to iOS devices that use a phone number as the Messages address.
The primary difference between iChat and Messages is that the latter can also message iPhones and utilize Apple's iMessage server, which is integrated into Mountain Lion and doesn't require that users keep the program open all the time. Messages is also present on iOS devices, whereas iChat is limited to just the Mac. Messages was also able to link to FaceTime for video calling, a feature iChat handles differently but separately from FaceTime. The ongoing issue, however, is that iChat is no longer supported and will eventually lose some of its functionality if Apple's arrangement with AIM (which currently hosts all iChat services) should ever change.
Lion users are not required to upgrade to Mountain Lion to use most of the same functionality Messages offered, but at $20 those who can update to it may want to do so in order to keep the Messages features (and gain other Mountain Lion features) they currently have. The update to Mountain Lion is Apple's first exclusively-downloadable system update (Lion was offered on a USB thumb drive for those who didn't want to download it) and is thus only available through the Mac App Store.
Users must already be running at least OS X 10.6.8 (Snow Leopard) in order to upgrade to Mountain Lion. Those on earlier systems can call Apple's telephone sales and order a DVD of Snow Leopard for $30 (plus shipping) in order to update their Intel-based Macs to the point where they can run the Mac App Store.