We will release an official announcement later today but our tests have shown performance and timing issues with Cubase, Nuendo and Sequel on Windows 10 (build 10240) systems.
Also, the latest Quicktime 7.7.7 cannot be installed on a Windows 10 system which basically removes the video support in Cubase and Nuendo.
While these issues did not occur on all systems we tested with, we can only recommend to wait.
In addition, the Yamaha Steinberg USB and Firewire drivers also show issues with sample rate switches and thus are not fully compatible either.
More information will follow as soon as we know more.