Here's the statement that NI has just released:
After intensive testing and close collaboration with Apple, we're happy to report full compatibility and highly stable audio performance with all of our current-generation hardware and macOS Sierra.
However, the following discontinued devices will not be supported on macOS Sierra, or future versions of macOS.:
First generations of TRAKTOR KONTROL S4 and TRAKTOR AUDIO 2
TRAKTOR AUDIO 8 DJ
TRAKTOR AUDIO 4 DJ
TRAKTOR AUDIO 2 DJ
AUDIO KONTROL 1
GUITAR RIG MOBILE I/O
GUITAR RIG SESSION I/O
RIG KONTROL 2
RIG KONTROL 3
KORE 2 Controller
MASCHINE hardware (all generations) is not affected.
If you own any of the above devices, we recommend that you continue to use them on your current OSX version. Please understand that since these devices are no longer supported by NI, we cannot guarantee performance or compatibility with macOS Sierra, or future versions of macOS.