When LibreOffice was announced, Canonical was one of the first companies to support it. Mark Shuttleworth said that Canonical will look at LibreOffice to replace OpenOffice in upcoming releases of Ubuntu.
In a message to the ubuntu-devel mailing list, Matthias Klose, wrote that they are replacing OpenOffice with LibreOffice for Ubuntu 11.04 Alpha 2, which is scheduled for release on 3rd February. However, unlike what many has been saying, this does not mean that Ubuntu 11.04 has dropped OpenOffice in favor of LibreOffice.
The final decision on whether to go with OpenOffice or LibreOffice has not been taken yet. LibreOffice has been included in Alpha 2 merely to give it a run to see if it is ready for inclusion in the final release of Ubuntu 11.04.
For the record, LibreOffice is a fork of OpenOffice being developed by former OpenOffice developers after Oracle asked them to leave following their creation of The Document Foundation.