Plymouth will not become the default boot screen in Ubuntu 9.04, but it's planned for integration with Ubuntu 9.10. In the meantime, however, a semi-official PPA (Personal Package Archive) will be created on Launchpad to house some experimental packages.
The Plymouth PPA will contain an updated kernel that supports kernel mode-setting, updated X.Org, the latest DRM bits, Plymouth itself, and a few boot plug-ins.
As we shared with a closer look at Plymouth, this is an open-source Red Hat project that has replaced RHGB (Red Hat Graphical Boot) in Fedora and eventually within Red Hat Enterprise Linux. Plymouth uses kernel mode-setting to provide a cleaner boot experience with minimal flickering of the display since the display only needs to set its mode once. Plymouth can also be tightly integrated with the GNOME Display Manager. We also have a video of Plymouth in Fedora 10 final.
There is an Ogg video of the Plymouth discussion that took place at last week's Ubuntu Developer Summit. Goodbye USplash!