Will the S9 be ready for OS High Sierra?

Should be, but with the way Apple keeps their sw updates in house, it may take some days or weeks to get it all synced.  I always stay an OS behind for my DJ laptop because of the likelihood of problems when a new OS comes out. 

We'll make any announcements concerning the update here as we move forward.

DjNickScott, it's in your best interest to update to OSX High Sierra after PioneerDJ (or any software company you rely on) creates a patch that supports that OS update.

The last thing you would want is to update your computer and end up with broken software and a gig the next night.