Early this year came the announcement of Ubuntu planning to switch to systemd following the Debian announcement that they would adopt systemd. Following that announcement it said the systemd transition would become before Ubuntu 16.04 LTS. Based upon the latest discussions, it looks like Ubuntu 15.04 could be the first release moving over to systemd.
Ubuntu developers are still working on migrating to systemd and ensuring compatibility with contained software, but so far things seem to be coming together. For developers and early adopters, systemd already works decent on Ubuntu 14.10.
Among the bugs that need to be addressed for the switch to happen is needing some AppArmor fixes, support for Ubuntu working in a LXC container with systemd, working cryptsetup integration with systemd during the boot process, and other changes. Some of the other work needed includes bringing up the network enablement in a good manner, NFS improvements, improving Plymouth integration, validating behavior for various packages, etc. While there's a lot of work that needs to be done to clear it for integration, the consensus expressed during today's Ubuntu Online Summit was, "generally we are ready to switch now."
Those wishing to find out more about the bugs and other issues that need to be addressed for systemd on Ubuntu, see the Ubuntu Online Summit session notes.