Despite your best efforts to try out the beta Messages application and help Apple out, you’re about to have your application pulled if you haven’t yet upgraded to Mountain Lion. Asinine, we know.
You have exactly seven days to upgrade your Mac to Mountain Lion, and if that’s an impossibility because your hardware doesn’t support the update, then you’re gonna have to go spend some coin on a new machine, or install some alternative. Also asinine, we know.
At this point, we have no idea if iChat will be fully restored to its previous state, but by the sounds of it, Messages will self-destruct the moment the beta expires. Did we mention how asinine this is yet?