14 DAY TRIAL // Ubuntu 14.04 LTS (Trusty Tahr) development might have entered feature freeze, but the Linux kernel freeze is still pretty far away. This means that the Ubuntu developers are constantly upgrading the Linux kernel to the latest version released by Linus Torvalds and company.
Older builds of Ubuntu didn't integrate the most recent Linux kernel available at that time, and this has been a point of contention for some time. In recent history, that trend has changed, and Ubuntu developers are now working hard to integrate the bleeding edge into their operating system.
As it stands right now, the latest stable branch of the Linux kernel is 3.13.x and a number of point releases have already been made available. The latest iteration, Linux kernel 3.13.5, has been adopted for Ubuntu 14.04 use and it's likely that we will see quite a few more kernel updates before the kernel freeze is in place.
“The 3.13.0-12.32 Trusty kernel is available in the archive. It's pulled the v3.13.4 upstream stable updates. We have also queued the next v3.13.5 upstream stable patches and anticipate this to be uploaded shortly. Our unstable branch has also been rebased to track the latest v3.14-rc4 release,” said Canonical's Joseph Salisbury in the official mailing list.
It's very likely that the final version of the Linux kernel that will eventually be implemented in Ubuntu 14.04 LTS (Trusty Tahr) is the current stable one, 3.13.x. Sure enough, a number of updates will still be pushed, but getting the new 3.14.x is going to be hard.
As you can imagine, Ubuntu developers are at Linus Torvalds’ mercy. So far, he has made available four release candidates in the 3.14 branch and it's impossible to predict how many more there will be. If he releases the kernel in time for the Ubuntu freeze, maybe the developers will get enough time to test it. Ubuntu kernel final freeze should arrive on April 3, which is still 5 weeks away.
Ubuntu 13.10 (Saucy Salamander) featured Linux kernel 3.10, but the developers never got a chance to switch to 3.11. The 3.10.x reached end of life quickly, but Canonical picked up the maintenance, mainly because they were already doing that for the operating system.
On the other hand, Linux kernel 3.12.13 has been announced as a long-term release, which means that the 3.13 branch might be one of those that will be very short-lived, and Canonical might have to pick up the maintenance for a kernel that has reached EOL.
We'll keep you apprised if any dramatic changes appear on the Linux kernel front for Ubuntu 14.04 LTS.