Ubuntu team is already planning for 10.04 LTS, which will see the light of day in April 2010
Ubuntu 10.04 (codename Lucid Lynx) LTS will be released Next year on April 29th.
Ubuntu 10.04 Release schedule
December 3rd, 2009 – Alpha 1 release
January 7th, 2010 – Alpha 2 release
February 4th, 2010 – Alpha 3 release
March 4th, 2010 – Beta1 release
April 1st, 2010 – Beta2 release
April 15th, 2010 – Release Candidate
April 29th, 2010 – Final release of Ubuntu 10.04 LTS
Links:
[1] http://www.geekinside.org/drupal/blog/2009/september/25/ubuntu-1004lucid-lynx-release-schedule
[2] http://www.geekinside.org/drupal/sites/default/files/lynx-cubs.jpg
[3] https://wiki.ubuntu.com/LucidReleaseSchedule