'Added to the Ubuntu meta package, the new Unity 8 desktop session will be available to try on all new installs and upgrades of Ubuntu 16.10, but only as an alternate login session to Unity 7. Unity 8 is not -- repeat: not -- going to be the default session in this release. Shipping it as a preview session is a great idea. It means to try Unity 8 on Ubuntu 16.10 you won't need to install a set of packages, or faff around with special set-up, or add a PPA. When at the Unity Greeter (aka the login screen) just click the session selector button, followed by 'Unity 8,' and then proceed to login as normal.'

-- source: https://linux.slashdot.org/story/16/10/06/1650200

Cheers, Peter