As you may know, Ubuntu Touch, Canonical’s mobile operating system, is currently based on Ubuntu 15.04 Vivid Vervet, only the development branches using Ubuntu Wily for now.
Canonical’s not planning to upgrade the Ubuntu Touch RTM branch to Ubuntu 15.10 yet, because this may cause issues with the Ubuntu Phones from Bq and Meizu.
For now, all the changes are performed to the stable, rc and rc-proposed branches, all being based on Ubuntu 15.04 Vivid Vervet.
As a reminder, Ubuntu Touch is a stable operating system, but it is not mature enough, compared to Android and iOS. For now, there are three Ubuntu Phones: Bq Aquaris E5 HD, Bq Aquaris E4.5, Meizu MX4, but the system is also officially supported on the LG Nexus 4 device.