As you may know, Canonical’s plan is to use Kernel 4.2 as default on the final version of Ubuntu 15.10 Wily Werewolf system.
The developers are already working towards this direction. Recently, they have announced that Kernel 4.2 RC6 has been added to the Wily unstable branch. Most likely, Kernel 4.2 stable will be released in about two weeks.
It is important that Kernel 4.2 gets released before the 8th of October, when the Kernel Freeze gets activated.