Through the wonderful ZFS On Linux project there is a native port of the ZFS file-system driver to Linux natively (unlike the ZFS FUSE implementation) but due to the GPL vs. CDDL licensing issue it can't be mainlined into the Linux kernel.
Mark Shuttleworth sent out a brief mailing list message today responding to a user interested in making ZFS Snappy support for Ubuntu. Mark wrote, "If it's ZFS you're after, it will be included in Ubuntu as standard in due course."
By "standard" he presumably means that Ubuntu will maintain a DKMS kernel package for it in the official Ubuntu archive and perhaps we'll see that package installed by default for Ubuntu Server, but that it wouldn't be directly patched into their kernel. That's what I'd assume at least given the license issues. Ubuntu wouldn't support ZFS for the root file-system, but could be useful on Ubuntu Server for some secondary drives with RAID-Z.
Soon as we have more info on Ubuntu's ZFS plans we'll certainly pass it along. Some recent ZFS Linux file-system benchmarks can be found within Running ZFS On The Linux 4.1 Kernel.
Update: Gentoo developer and ZFS On Linux contributor, Richard Yao, has added some insightful comments. According to him, Ubuntu 16.04 could potentially have ZFS included within Ubuntu's Linux kernel build and that it would be legally allowed.