SharePoint 2016 RTM and keys are available for downloading in MSDN!
It is not officially anounced yet. I think the official anouncement of the general availability will be in a few hours on The Future of SharePoint event. If you haven’t registered for it yet, I would recommend to do it. Jeff Teper, the father of SharePoint, will unveil Microsoft vision and roadmap for SharePoint and OneDrive for Business on this event.