I have not officially begun to test / port the MU-2 to X-Plane 12; HOWEVER, I have been testing it regularly in X-Plane 12 and the good news is that it seems at first glance....to be mostly functional....FOR.....daytime flight. I say this because the biggest change in X-Plane 12 is the new atmospheric and lighting engine..and this requires new "directive commands" for lighting that were not present in X-Plane 11. The nightlighting is practically non-existent until I make the required changes. Also I have to make some notable changes to take advantage of the rain effects....so the V11 version "in V12" will not have the new windshield effects. So....daytime and dry seems to be mostly OK using the V11 version in V12. I know there are some turbine engine changes also I have yet to test...so unsure what their effect will be.
The plan is to get the next release patch, 2.0.3 out for V11 (relatively imminent), and then begin the official port / testing process for V12. Probably will begin the work next Monday. I do not expect it to be terribly long. Chances are XP12 will go through some growing pains anyhow and I'll be right there alongside the process testing/tweaking the Moo.
Experienced XP users should know to keep their XP11 versions around until they're fully happy with V12.
Here's a few screenshots of the Moo in V12. Not terribly bad, but I may tweak it after I get going. Things tend to look a little bit shinier in V12...but also brighter, which is good.