Office 2016 "RTM" was released to the public on September 22 2015.
Office 365 Home, Personal, and University subscribers can download it now by logging into their account online and clicking Install, or wait until October 1 2015 for the automatic update.
Office 2016 is expected to be released to Office 365 Business subscribers and volume licenses in February 2016. If you are on First Release, use the install link for the next version of Office.Anyone who used the Preview can leave it installed and will remain in the early release 'branch' (similar to Windows Insider program.) Office 2016 Preview is now available to the public.