Ubuntu 16.04 LTS Is Continuing To Prep ZFS Support
Chad Miller of Canonical shared that "ZFS is right now 90% ready on (what will be) Ubuntu 16.04." There still are new ZFS packages to land in the Ubuntu 16.04, but Chad has the current packages queued up in a PPA. These packages will allow for installing Ubuntu to a ZFS partition, but an EFI partition is still needed. Additionally, there's no support in Ubuntu's Ubiquity graphical installer for setting up an easy ZFS-based system.
More details via this Google+ post. Sans the official distribution support, you can already use the ZFS file-system on the distribution of your choice using the wonderful ZFSOnLinux.org.
EXT4 will obviously be the default file-system still for Ubuntu 16.04 LTS. There's also still nothing out on the horizon indicating Oracle might be prone to re-licensing the ZFS to something GPL-compatible rather than the CDDL so that it would be accepted in the mainline kernel.