I just upgraded to Sierra and now I kernel panic (stack trace right back to the promise pegausus J4 driver) when I book if the J4 is connected.
I have seen responses to El Cap questions just brushing this off as an EOL product, but it's only 3 years old! Not to mention, it wasn't cheap.
I'm hoping that there is some chance someone either plans to fix the driver or knows a workaround.