The Ubuntu team is already planning for the release of Ubuntu 11.04 “Natty Narwhal”, it will be released in April 2011. Here is a list of dates when the Alpha and Beta versions will be released.
Ubuntu 11.04 “Natty Narwhal” will be released on the 28th of April 2011.
Release dates:
December 2nd 2010 – Alpha 1 release
February 3rd 2010 – Alpha 2 release
March 3rd 2011 – Alpha 3 release
March 31st 2011 – Beta 1 release
April 14th 2011 – Beta 2 release
April 28th 2011 – Ubuntu 11.04 Final release
Complete Natty release schedule HERE