Ubuntu team is already planning for 9.10, which will see the light of day in October 2009. The desktop side will focus on beautification and an improved boot-up experience; the server side will target cloud computing.
Ubuntu 9.10 (codename Karmic Koala) will be released this year on October 29th.
Ubuntu 9.10 Release schedule
May 14th, 2009 - Alpha 1 release
June 11th, 2009 - Alpha 2 release
July 23th, 2009 - Alpha 3 release
August 13th, 2009 - Alpha 4 release
September 3rd, 2009 - Alpha 5 release
September 17th, 2009 - Alpha 6 release
October 1st, 2009 - Beta release
October 22nd, 2009 - Release Candidate
October 29th, 2009 - Final release of Ubuntu 9.10