I've just posted Magma for Squeak 3.9 (7057) on the MagmaTester project.
The upgrade to work with 3.9 was relatively uneventful; the biggest change was to include serialization of Pragmas in CompiledMethods. There were also some methods renamed.
In order to have just one code base, I had to put a couple of "is3dot9" checks into the code. And due to the extension methods on Pragma and MethodProperties, Monticello will also report a warnning now when trying to load into a 3.8 image. So, for now, I've just put it into MagmaTester to see what anyone else thinks; deal with a couple (literally, two, I think) of ugly conditionals and a warning when loading for 3.7 and 3.8, or maintain two versions (branches) of the code..
I really don't want to maintain two branches, but yet the load warning might be a real turn off for (new) people unless they know to expect it somehow.. Of course, if 3.9 is the future then it won't be an issue.
Enjoy, and thanks for any feedback..