When Apple unexpectedly announced OS X Mountain Lion yesterday, they offered Mac users a taste of things to come in the form of a beta version of the new Messages app. The app works just like Messages for iOS, in that it allows users to send text, video, and picture messages to any other device running the app – Mac, iPhone, iPod Touch, or iPad.

The beta release of the app excited many Lion users. Today’s news, however, may put a damper on many users’ excitement. It seems that once the beta is over and Mountain Lion is released, Messages will no longer run on Lion. French tech blog Consomac (Google Translation) went digging through the code for Messages and found an error message that will be displayed on Macs running Lion once Mountain Lion is released. Check out a screen shot below, courtesy of Consomac:

Now, for users who plan on upgrading to Mountain Lion, this is no problem. Messages will be fully functional again once their upgrade is in place. Those who weren’t planning to upgrade – or those who can’t because their Mac is not compatible – are left out in the cold, however.

It’s not at all clear why Apple will be disabling Messages for Lion – unless it’s just as an incentive to upgrade to Mountain Lion. I sent a message to Apple asking for clarification, but have not yet received a reply. In the meantime, Lion users still have several months left in which to enjoy the beta version of Messages. Mountain Lion is currently slated for a “late summer 2012” release.