There is now a Launchpad specification to evaluate Plymouth for Ubuntu and potentially use it to replacement the current USplash project. Canonical's Matthew Paul Thomas confirmed on the developer mailing list that Plymouth will also be discussed at the Ubuntu Developer Summit taking place in early December.
It certainly would be interesting if they switched to Plymouth in Ubuntu. If they did so in time for Ubuntu 9.04 it would mandate they use at least the Linux 2.6.29 kernel in order to have the needed kernel mode-setting support. Right now Fedora 10 is the only distribution shipping Plymouth. To see what Plymouth looks like, check out our Plymouth video.