The Ubuntu project has announced that Dapper Drake release will be delayed for six weeks from April 20th to June 1st 2006.
According to the announcement, the additional time will be use to devote bug fix, improving localisation for Asian languages, add XFCE desktop enviroment and to ensure that Dapper Drake will be LSB certified among others.
You can get the new Dapper Drake release schedule at this location : https://wiki.ubuntu.com/DapperReleaseSchedule