Hi Ivan, the main things what I did for 1.2 were SQL optimizations. With simple DOS attacks with 3 consecutive users I was able to lift queries per second over 8.5 times faster. And actually had only one consecutive connection open with initial tests where the 8.5 times faster was done with 3 consecutive connections doing DOS on it. And those were just easy tests, in general. The performance optimizations are huge. Like 'mark all read' literally takes seconds anymore even you would have 150k unread threads. (Obviously server performance has huge factor in it)
You can get 1.2.1 clone 1.2.1-pl from
https://github.com/modxcms/Discuss (it has transport package under _packages/
The 1.2.1 will take a while to install if you have big forum. Also could be beneficial to run core/components/discuss/includes/fix.maps-closures.php if you have loads of boards. It fixes board maps and closures in the database. This should have been in the transport package but with certain servers the upgrade might die to rebuild of few tables which can take a while.
When packages will be available in package manager? No idea, could be then when we get ttyl updated. But I try to push team MODX to publish the package. It was designed to be fix for here but obviously the same bugs get fixed in the main package also.