A new version of rekordbox 4.0.7 was released on Feb 18, 2016.
With a DJM-900NXS2 connected to a computer via USB you can control up to 4 units of CDJ-2000NXS2 via PRO DJ LINK.
(Please update the DJM-900NXS2 firmware to 1.09 or later. The “Connection Guide” is here).
Compatible devices added:
-Crossfader characteristics in Export mode.
-Crashed when MyTag was revised when synchronised to MyTag data on a USB device when the USB device was recognised.
-Performance became slow after using rekordbox with certain types of controllers.
-Preview playback volume was not adjusted by the Master volume.
-Improved stability and fixed other minor issues.