Microsoft has a private Office 2016 beta group who have access to the next version of Office, and if you feel bummed that you were not included in the group, there is now a way to download it.
If you head to this link, you can now sign up for the Office 2016 preview and download the bits right now. After signing the NDA, you will be taken to a dashboard where you can download the January technical preview of Office 2016. During the sign-up process, it will ask you to enter the email address where you received the invitation to join the program but if you enter any email address, you are automatically accepted into the program. We are not sure if this is a bug, as it would appear that they do try to authenticate the email to the user before offering access, or simply a backwards way to reach the open beta, either way, it allows anyone to download the pre-release software.
Update, it seems that MS has taken the download offline again .. ?