Canonical has released the first beta of the new Ubuntu 16.10 Yakkety Yak but only for the opt-in flavors, namely Ubuntu MATE, Kubuntu, GNOME, Lubuntu, Ubuntu Studio, and Ubuntu Kylin. It seems that Xubuntu is not included in the first Beta release.
Ubuntu itself is not available as Beta 1, and will only be released as Final Beta, which will be the second and last Beta. 
As you may know, Canonical will try to replace Upstart with systemd, unify and fix networking configuration through the implementation of the “netplan” project that we will see in the final release of Ubuntu 16.10 Yakkety Yak.
Apart from these, most of the software packages have been updated with their latest versions such as: LibreOffice 5.2 and GCC (GNU Compiler Collection) 6.2.0, as well as the latest stable GNOME 3.20 Stack release.
Linux kernel 4.6.7 should be coming to Ubuntu 16.10 sometime next week, which means it won't be in Beta 1. However, the final version of Ubuntu 16.10 will be powered by Linux kernel 4.8, which is currently being released as Linux Kernel 4.8 Release Candidate 3.
