Some had hoped the interesting systemd project would replace Upstart in Ubuntu 11.10, but don't count on it. It doesn't look like it's happening. The reasons being heard, according to the Ubuntu camp, is that changing out Upstart now with Ubuntu 12.04 being an LTS (Long-Term Support) release is too close and that systemd doesn't have any advantages over Upstart.
The earliest then that we may see Ubuntu switch over to systemd would be Ubuntu 12.10 in October of 2012, which would be one release past their next Long-Term Support offering.
See this mailing list thread for the discussion taking place on the web.
For those wondering about the features or design of systemd, see the previous Phoronix posts on the matter. In particular, this recent posting. The first major Linux distribution to be deploying systemd will be Fedora 15 when it's released in May.