It appears that Safari v80 has been leaked with one thread on FunMac.com posting a small review of the new build.
Safari v80 is said to incorporate a preference for .Mac bookmark Syncronization as well as "Autotabs" allowing you to open a folder of bookmarks into a set of tabs at once.
Another report indicates that the install process has been modified -- with the upgrade package installing Webkit and the Foundation Frameworks in /System/Library/Frameworks instead of within the actual application. One user speculates that this may make it easier to share these resources amongst other Apps, and also provides a single location for upgrades to provide system-wide updates to the Webkit.