With the Linux 3.13 kernel nearly out, the kernel team at Canonical is preparing to submit their first 3.13 kernel package into the Ubuntu 14.04 Trusty archive for testing ahead of the April distribution release.
The official kernel to ship in Ubuntu 14.04 LTS is likely going to be a Linux 3.13 "Franken" kernel. There's a chance they might land the Linux 3.14 kernel but since this is a Long-Term Support release Canonical has been hesitant to commit to shipping it. Instead their 3.13 kernel will become a "franken" kernel as they will end up carrying many of the Linux 3.14 patches back-ported themselves into their kernel, since they need updated hardware support and other changes not landing until Linux 3.14. For 3.14 there should be better Intel Broadwell support, continued work on open-source graphics drivers, file-system improvements, and many other changes.
Confirmation of their move from Linux 3.12 to 3.13 in the Ubuntu 14.04 archive was made at this week's kernel team meeting. "We've finished cleaning up some DKMS packages for Trusty and are preparing for our first v3.13 based kernel upload to the archive. This is specifically based on the latest v3.13-rc7 upstream kernel."