Unfortunately SCOTUS will never rule on most of this law.
We might get relief for the assault style firearm section and maybe the standard capacity magazine ban. There might also be some relief long down the line for approved firearm rosters.
But the red flag expansion, more arduous safety course, limits on juvenile use, homemade firearm restrictions, 3D printer/CNC use, and more and more will not see relief from SCOTUS anytime in the next few decades. Likely. Maybe red flag laws sooner.
We MAY get state or circuit relief on some of the smaller parts of the law. But this is a huge law with many tentacles in various sections of MGL. It will be hard to dismantle even most of it.