taken from wiki....
HBO has officially confirmed that there will be a sixth season of Curb Your Enthusiasm.[1] It is set to debut on September 9th, 2007, at 10 P.M. Eastern on HBO.
Guest stars in the upcoming season will include: Vivica A. Fox as part of a family who moves into the Davids' home following a natural disaster;[2] Barbara Boxer as herself;[3] and Steve Coogan as a psychiatrist.[4].
It is unknown if the sixth season will be the last. In an interview on April 25, 2007 with The National Ledger, Cheryl Hines confirmed that Larry David "seems to think this might be the end-end", but she is "trying to talk him out of it".[5] On his website, long time Curb Your Enthusiasm director Robert Weide confirmed that this season would be his last involvement with the show.[6]