Hi, i’ll soon buy a new Imac with osx Sierra 10.12 inside. Does Cubase pro 8.5 (last maj) will work ?
Or do you plan to create a new maj for Sierra ?
This is the latest information Steinberg posted about Sierra. Posted on September 12, 2016.
Regards 
CuBase Pro 8.5 is now compatible with Sierra.
Latest announcement as of November 17 2016:
https://www.steinberg.net/en/newsandevents/news/newsdetail/article/steinberg-software-products-compatible-with-macos-1012-sierra-3977.html
Knowledge Base article:
https://www.steinberg.net/nc/en/support/knowledgebase_new/show_details/kb_show/macos-sierra-steinberg-software-compatibility-information.html