14 DAY TRIAL // The Ubuntu 15.10 development cycle is coming to an end, and the operating system has reached the final kernel freeze milestone. No more upgrades are made past this point, and only bug fixes are permitted.
The Ubuntu development cycle is not in sync with the Linux kernel, so the latest version released is not usually implemented. As it stands right now, the Linux kernel used in Ubuntu 15.10 is 4.2, and it's possible that a new one will be made available soon after launch, maybe right before.
When a project hits one of these freeze milestones, whether it's for software stacks or the kernel, no more upgrades are being made. This allows developers to properly test everything and make sure that everything is in order for the launch.
Ubuntu usually ships with a specific branch of the kernel and then sticks with it. Even if a new version of the kernel is released, they don't usually upgrade it, at least not for the non-LTS versions of Ubuntu which are only supported for nine months. On the other hand, the Ubuntu LTS versions do get kernel upgrades with each new point release.
Ubuntu 15.10 is shipping with Linux kernel 4.2
The fact that the kernel freeze is in effect right now for Ubuntu 15.10 means that we won't get to see any more changes. That was almost certain a couple of weeks ago, but it's now officially confirmed.
"We are approaching Wily Kernel Freeze this Thurs Oct 8, ~2 days away! If there are any patches that need to land for 15.10, please get them submitted immediately. Following the Kernel Freeze deadline, all patches are subject to our SRU policy and could miss the release," wrote Canonical's Joseph Salisbury a few days back.
The final version of Ubuntu 15.10 (Wily Werewolf) is expected to land on October 22.